Mutagenesis, Vol. 16, No. 4, 345-351,
July 2001
© 2001 UK Environmental Mutagen Society/Oxford University Press
Evaluation of the cytogenetic damage induced by the antihypertensive drug nimodipine in human lymphocytes
1 Departamento Biología Animal y Genética, Facultad de Ciencias, Universidad del País Vasco, Apartado 644, 48080 Bilbao, Spain, 2 Instituto Portugués de Oncología, Porto, Portugal, 3 Departamento Farmacología Clínica y Dietética, Escuela de Enfermería, Universidad del País Vasco, Bilbao, Spain and 4 Departamento Especialidades Médico-quirúrgicas, Facultad de Medicina y Odontología, Universidad del País Vasco, Bilbao, Spain
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The aim of this work was a study of the genotoxic potential of chronic long-term therapy with the antihypertensive drug nimodipine by measures of sister chromatid exchanges (SCE) and micronuclei (MN) in peripheral human lymphocytes of patients with long-term exposure to this drug. Peripheral human lymphocytes of control individuals exposed in vitro to nimodipine were also studied to assess the effect of the drug itself. Fluorescence in situ hybridization (FISH) with a centromeric probe was performed to determine the origin of the induced MN. The in vivo study was carried out on five patients under antihypertensive treatment with nimodipine. The in vitro study was performed on five control individuals by adding the drug to the culture medium at a final concentration similar to the levels found in plasma (controls/medium). The in vivo study showed no genotoxic effects of long-term therapy with nimodipine because the frequencies of SCE and MN in exposed patients did not show significant differences as compared with control individuals. A statistically significant increase in the frequency of MN was detected in controls/medium as compared with control individuals without the drug. FISH analysis revealed statistically significant differences with respect to the frequency of centromeric signals in nimodipine-induced MN in vitro. With regard to the in vivo results, chronic long-term therapy with nimodipine is not associated with increased genotoxicity. The differing results in vivo and in vitro could be due to extensive metabolism of nimodipine, indicating that the cytogenetic effect observed was due to the drug itself rather than its metabolites or to an adaptive response to nimodipine in vivo.
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Introduction |
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Arterial hypertension and blood pressure regulation are a related disease and physiological end-point which have received considerable attention from every conceivable medical research angle. There are numerous reasons for this, not least of which is the fact that hypertension is an extremely prevalent condition in industrialized countries, accounting for more than 5% of total deaths world wide (Schork et al., 1999
; Pardell et al., 2000). The duration of the pharmacological treatment of hypertension may last for decades and, therefore, patients are exposed to prolonged contact with these drugs. According to Furberg et al. (1996) long-term treatments require documentation of long-term safety and efficacy, including sensitive indices of genotoxic damage.
Micronuclei (MN) are acentric chromosome fragments or whole chromosomes that are left behind during mitotic cellular division and appear in the cytoplasm of interphasic cells as small additional nuclei. The measurement of MN combined with fluorescence in situ hybridization (FISH) with centromere-specific DNA probes allows discrimination between MN due to fragments (clastogenic damage) and MN containing whole chromosomes (chromosome loss), since the presence of a hybridization signal in a MN is a direct measure of the presence of a centromere (Eastmond et al., 1995; Zijno et al., 1996; Tucker et al., 1997). This methodology is being increasingly used in monitoring studies (Ramírez et al., 1997; Migliore et al., 1999a; Thierens et al., 1999; Andrianopoulos et al., 2000; Touil et al., 2000).
Sister chromatid exchanges (SCE) are events that involve breaks in both chromatids of a single chromosome, at coincident locations, with subsequent interchange and repair (Latt et al., 1981). SCE have been evaluated in numerous studies involving human exposure to therapeutic compounds (Sarto et al., 1990; Awara et al., 1998; Migliore et al., 1998; Lanza et al., 1999; Ahmad et al., 2000; Pilger et al., 2000).
In a previous work (Télez et al., 2000) we applied SCE and MN combined with FISH assays to study the genotoxic potential of the ß-blocker antihypertensive drug atenolol following in vivo and in vitro human exposure. The results obtained showed that chronic exposure in vivo to atenolol resulted mainly in the induction of chromosome loss, so an aneugenic effect could be predicted. Apart from this work, a few studies on other different antihypertensive drugs have reported positive results from animal experiments using different test systems (Glatt and Oesch, 1985; Grisolia and Takahashi, 1991; Chlopkiewicz et al., 1995; Marczewska and Koziorowska, 1997; Chlopkiewicz, 1999; Nesterova et al., 1999). However, the published literature concerning genotoxic studies on antihypertensive drugs in general is poor. Taking into consideration that these drugs are administered to a wide spectrum of patients, sometimes in high amounts and for a significant period of a person's lifetime, the previous results reiterate the need to extend this type of study, mainly in humans, to make a careful evaluation of the cost–benefit ratio.
For this purpose we chose the group of antihypertensive drugs termed calcium antagonists. They constitute a biochemically and pharmacologically heterogeneous group of drugs that modulate the transmembrane influx of Ca2+ into contractile cells of the vasculature. Recent epidemiological reports have raised widespread concern in the medical community about a possible link between calcium antagonist use and the development of cancer as a result of modulating cellular apoptosis (Pahor et al., 1996a, b; Fitzpatrick et al., 1997). In contrast, several subsequent observational studies, long-term controlled clinical trials and preclinical toxicological studies showed no evidence supporting the hypothesis that calcium antagonists may be carcinogenic (Olsen et al., 1997; Rosenberg et al., 1998; Mason, 1999; Meier et al., 2000).
Among the calcium antagonists nimodipine is a calcium slow channel antagonist of the dihydropyridine class which has been found to have markedly beneficial therapeutic value in treating hypertension (Dollerf, 1991; Kazda, 1994). The chemical structure of nimodipine [1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid 2-methoxyethyl-1-methylethyl ester] is shown in Figure 1. There is no evidence of mutagenic activity in animal experiments or in the Ames test (Dollerf, 1991).
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We here report our data from a study of the genotoxic potential of chronic long-term therapy with nimodipine, which was tested for its ability to induce SCE and MN in cultured human peripheral blood lymphocytes of treated patients and in vitro exposed control individuals. The origin of MN was determined by FISH with a probe detecting all human centromeres. The use of multiple end-points in the same population is recommended by several authors because it can provide valuable information relative to the sensitivity of each end-point as well as to the potential hazard for the population (Carrano and Natarajan, 1988
; Tucker et al., 1997; van Delft et al., 1998). |
Materials and methods |
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Sample
The sample was made up of two different groups: five hypertensive patients and five control individuals, matched with respect to sex, age and smoking habits (in this present study all individuals were non-smokers). Patients (four females and one male) ranged in age from 70 to 82 years with an average age of 77 years. The doses ranged from 60 to 90 mg nimodipine/day (two to three tablets) taken by oral administration. The mean duration of treatment was 3.1 years (2–5 years). None of them were undergoing other medical treatments. They did not have a previous history of exposure to genotoxic compounds or recent X-ray examination. Each patient was given a code number (P1–P5) according to the sequence of blood collection. Control individuals (three females and two males) had an average age of 70.8 years. All of them were healthy individuals not undergoing any pharmaceutical compound intake, X-ray exposure or alcohol and/or drug consumption in the recent past. Each control individual was given a code number (C1–C5) according to the sequence of arrival at the laboratory. Informed consent was obtained from all individuals taking part in the study.
Blood collection and cell cultures
Several cultures were established depending on the group of people. For patients venous blood was taken from each subject and duplicate whole blood cultures were set up. These cultures were numbered P1–P5. For control individuals two different cultures were performed. Venous blood was taken from each subject and duplicate whole blood cultures were set up, numbered C1/T-1–C5/T-1 (controls/T-1). Another set of cultures was performed by adding the chemical compound to the culture medium at the start of culture. Previously a stock solution of nimodipine (batch no. 273640C, purity 100.1; Bayer) had been prepared in methanol and kept in an amber glass volumetric flask. It had been stored in the dark under refrigeration to avoid possible decomposition. Working solutions had also been prepared in amber glass volumetric flasks by appropriate dilution just before use. Nimodipine was tested at a final concentration in the culture medium of 0.06 mg/ml. This was the average concentration found in patients after oral intake (these analyses were performed in the Department of Analytical Chemistry, University of the Basque Country, Spain). These cultures were numbered C1/medium–C5/medium (controls/medium).
Cytogenetic tests
Lymphocyte cultures were set up by adding 0.5 ml of heparinized whole blood to 4.5 ml of RPMI-1640 medium (Gibco) supplemented with 10% fetal bovine serum (Gibco), antibiotics (penicillin and streptomycin) (Gibco), glutamine (Gibco) and HEPES buffer solution (Gibco). Lymphocytes were stimulated by 4% phytohemagglutinin (Gibco). Nimodipine was added to those cultures numbered C1/medium–C5/medium.
For the SCE assay the cultures were incubated at 37°C for 72 h in the dark and 5-bromodeoxyuridine (Sigma) was added 24 h after initiation of cultures at a final concentration of 12 µg/ml. One hour prior to harvesting 0.4 µg/ml colcemid (Gibco) was added to arrest the cells at metaphase. For the MN assay the cultures were incubated at 37°C for 72 h. Binucleated cells were accumulated by adding cytochalasin B (Cyt-B) (Sigma) at a final concentration of 6 µg/ml (Surrallés et al., 1992) at 48 h following initiation of culture. At the end of the incubation time the cells were collected by centrifugation and for SCE resuspended in a pre-warmed hypotonic solution (0.075 M KCl) for 10 min and fixed three times in methanol:acetic acid (3:1). Cells were spread on slides, air dried and stained with fluorescent dye plus Giemsa (Perry and Wolff, 1974). For MN the cells were washed once in RPMI-1640 medium and then a mild hypotonic treatment (2–3 min in 0.075 M KCl at room temperature) was carried out. The cells were then centrifuged and a methanol: acetic acid (5:1) solution was added. This fixation step was repeated twice. Air dried preparations were made and the slides were stained with 10% Giemsa in phosphate buffer for 20 min.
Fluorescence in situ hybridization
For the identification of centromeres in MN FISH was performed with a digoxigenin-labeled probe for all human centromeres (ONCP 5095; Oncor), following the protocol recommended by the manufacturer. Slides were incubated for 30 min in 2x SSC, pH 7.0, and then dehydrated in a series of ice-cold ethanol washes (70, 80 and 95% for 2 min each) and dried at room temperature. The probe was diluted in Hybrisol VI (Oncor), denatured at 70°C for 5 min, applied to the slides, coverslipped and incubated overnight at 37°C in a humidified chamber. After hybridization slides were washed in 2x SSC, pH 7.0, at 37°C for 10 min and in phosphate-buffered saline at room temperature for 10–20 min. Detection of the digoxigenin-labeled probe was performed by layering of fluorescein-labeled anti-digoxigenin antibody (Oncor) for 10 min at 37°C in a moist chamber. Slides were counterstained with propidium iodide (Oncor) and mounted in antifade solution (Oncor) to preserve fluorescence. To evaluate probe hybridization efficiency metaphase spreads were also examined.
Slide scoring and statistical analysis
For the SCE assay a total of 50 well-spread metaphases of the second division were examined for each individual and type of culture on coded slides in a blind study. Statistical analysis for SCE was performed using the t-test. One hundred metaphases were also scored to determine the proportion of cells that undergo one, two and three or more divisions. The proliferative rate index (PRI) was evaluated according to the formula PRI = (M1 + M2 + M3)/n, where M1, M2 and M3 indicate those metaphases corresponding to the first, second and third or subsequent divisions and n is the total number of metaphases scored (Lamberti et al., 1983).
For the MN assay 1000 binucleated (BN) cells with well-preserved cytoplasm were examined for each individual and type of culture on coded slides in a blind study. The identification of MN was according to the criteria described in Fenech (1993). The distributions of the BN cells with MN (BNMN) and the total of MN obtained among the individuals studied were compared with the normal distribution by means of the Kolmogorov–Smirnov test of goodness of fit. Neither of them departed significantly from normality and therefore parametric tests (the t-test in this case) were adequate for statistical analysis of the results. In addition, a minimum of 500 lymphocytes were also scored to determine the percentage of cells with 1, 2, 3, 4 or >4 nuclei. A nuclear division index (NDI) was calculated according to the formula NDI = (M1 + 2M2 + 3M3 + 4M4)/n, where M1–M4 represent the number of cells with one to four nuclei, respectively, and n is the number of cells scored (Eastmond and Tucker, 1989).
For the FISH analysis a total of 50 MN for each individual and type of culture on coded slides in a blind study were analysed for the presence of a fluorescent signal. MN were classified as centromere-negative (CN–) or centromere-positive (CN+) by considering the presence of a hybridization signal in a MN as a direct indication of the presence of a centromere. Among CN+ MN signals of different intensities were found due to variable amounts of 
-satellite DNA on different human chromosomes. However, hybridization on metaphase chromosome preparations confirmed the extremely precise location of the signals only at the centromere, varying only in intensity. Statistical evaluation of the results was performed using the 
2 test.
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Results |
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The effect of nimodipine on the induction of SCE is summarized in Table I
. In this table the mean number of SCE per cell (± SE) and the PRI values obtained in patients, controls/T-1 and controls/medium are reported.
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The mean frequency of SCE was not significantly higher in patients compared with controls/T-1 (patients 8.71 ± 0.21 versus controls/T-1 8.40 ± 0.22, P > 0.05). When the SCE frequency in controls/T-1 was compared with that found in controls/medium it could be observed that the SCE values increased slightly when nimodipine was present in the culture medium but the differences were not statistically significant (controls/T-1 8.40 ± 0.22 versus controls/medium 9.91 ± 0.26, P > 0.05). These data for human lymphocytes demonstrate that nimodipine has little effect in inducing SCE in vivo and in vitro.
Concerning its cytotoxicity, measured as cell cycle delay, the PRI values did not show significant differences when patients were compared with controls/T-1 (patients 2.00 ± 0.15 versus controls/T-1 1.96 ± 0.07, P > 0.05), so nimodipine does not seem to show cytotoxic effects in vivo. However, the PRI value suffered a statistically significant decrease in controls/medium as compared with controls/T-1 (controls/T-1 1.96 ± 0.07 versus controls/medium 1.67 ± 0.06, P < 0.05), indicating cellular toxicity of nimodipine in vitro at the concentration tested.
A wide variability among individuals could be noted regarding both the mean frequency of SCE and the PRI value. Among patients the first variable ranged from 7.22 to 9.42 and the PRI values from 1.68 to 2.40. However, this variability did not seem to be related to age, sex, dose of nimodipine or duration of treatment. Among control individuals the mean number of SCE per cell ranged from 8.02 to 9.30 in controls/T-1 and from 8.76 to 11.54 in controls/medium and the PRI values ranged from 1.83 to 2.24 in controls/T-1 and from 1.47 to 1.85 in controls/medium. Despite the interindividual variability, all control individuals showed an increase in SCE values and a decrease in PRI values when nimodipine was added to the culture medium. The increase in the SCE frequency was statistically significant in individual C3, ranging from 8.98 in C3/T-1 to 11.54 in C3/medium (P < 0.01), and in individual C4, ranging from 7.16 to 9.36 when nimodipine was added to the culture medium (P < 0.01). These individuals were the males who constituted the control sample.
The results of the MN study are shown in Table II. This table shows the distribution of MN in the 1000 BN cells scored, the total number of MN, the total number of BNMN and the NDI values obtained in patients, controls/T-1 and controls/medium.
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The two variables analysed, total MN and total BNMN, were slightly increased in patients with respect to controls/T-1 but the differences were not statistically significant (patients 12.20 ± 2.35 and 11.40 ± 2.16, respectively, versus controls/T-1 10 ± 1.30 and 9.60 ± 1.21, respectively, P > 0.05 in both cases). When the means of total MN and total BNMN obtained in controls/T-1 were compared with those obtained in controls/medium the high increases observed showed statistical significance (controls/T-1 10 ± 1.30 and 9.60 ± 1.21, respectively, versus controls/medium 16.80 ± 1.46 and 13.80 ± 1.02, respectively, P < 0.01 for both variables). These data seem to indicate an effect of nimodipine in inducing the significantly higher frequencies of MN and BNMN in vitro.
The NDI measure showed statistically significant differences when patients were compared with controls/T-1 (patients 1.39 ± 0.07 versus controls/T-1 1.62 ± 0.05, P < 0.05). In the same way statistical significance was found when the NDI value in controls/T-1 was compared with that obtained in controls/medium (controls/T-1 1.62 ± 0.05 versus controls/medium 1.35 ± 0.05, P < 0.01). Accordingly, nimodipine seems to show cellular toxicity in vivo and, mainly, in vitro.
Variability among individuals could be observed in both groups. Among patients individual P2 presented the highest MN and BNMN frequencies (21 and 19, respectively) and individual P3 the lowest ones (7 and 6, respectively). The NDI values ranged from 1.20 for individual P5 to 1.60 for individual P3. However, as in the SCE assay, the variability observed did not seem to be related to age, sex, dose of nimodipine or duration of treatment. Among control individuals the total number of MN and BNMN ranged from 7 to 14 for both variables in controls/T-1 and from 12 to 21 and from 11 to 17, respectively, in controls/medium. In all control individuals the MN and BNMN frequencies increased and the NDI values decreased when nimodipine was tested in vitro. Individual C3 showed the greatest differences again, although they did not reach the significance level in this case.
Study of the nature of nimodipine-induced MN in vitro is presented in Table III. In this table the total number and percentage of CN– and CN+ among the 50 MN scored for each subject and for the total sample are reported. Only controls/T-1 and controls/medium were analysed for the presence of centromeric signals with a centromeric probe.
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In controls/T-1 50.80% of the MN were CN+, whereas 49.20% did not present hybridization signals, suggesting that they contain acentric chromosome fragments. When nimodipine was added to the culture medium the percentage of CN+ MN increased to 71.60% and the percentage of MN containing acentric fragments decreased to 28.40%. The differences in the percentage of CN+ MN between controls/T-1 and controls/medium were statistically significant (controls/T-1 50.80% versus controls/medium 71.60%, P < 0.001), suggesting an ability of nimodipine to induce chromosome loss in vitro at the concentration tested.
Low variability was observed in the percentage of CN+ MN among individuals. All of them presented similar rates, ranging from 44 to 54% in controls/T-1 and from 68 to 74% in controls/medium.
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Discussion |
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Concerning the results obtained in our in vivo study, chronic exposure to nimodipine is not associated with genotoxic effects because no significant increases in the frequency of SCE and MN were found in patients as compared with controls/T-1.
The results of the in vitro study were quite different. Nimodipine at a concentration similar to that achieved during in vivo therapy was incapable of inducing SCE in peripheral lymphocytes after exposure in vitro. However, nimodipine led to a statistically significant enhancement of the two variables studied in the MN assay, total number of MN and total number of BNMN. These data suggest that in vitro exposure to nimodipine results mainly in induction of chromosome loss. This suggestion was confirmed by FISH analysis using an -satellite probe for all human centromeres. The statistically significant differences in CN+ MN between controls/T-1 and controls/medium indicate more frequent involvement of aneuploidy (specifically chromosome loss) phenomena in the origin of nimodipine-induced MN in vitro. These results agree with those previously reported by the SCE assay.
Concerning cytotoxicity, measured as PRI in the SCE test and NDI in the MN technique, nimodipine showed cellular toxicity in vivo only in the last assay. In vitro, however, nimodipine induced statistically significant decreases in both the PRI and NDI indices.
Different results in vivo and in vitro could be explained by a difference in the metabolism of the compound in vivo. Nimodipine is subject to extensive presystemic hepatic metabolism. Nimodipine kinetics are linear in the dose range 10–90 mg. Less than 1% of the drug appears in the urine as unchanged drug. About 80% of an orally administered dose appears in the urine in the form of nine inactive acidic metabolites (Dollerf, 1991). In vitro assays cannot take fully into account human body absorption, distribution, metabolism and excretion of a pharmaceutical (Aaron et al., 1993; Müller et al., 1999). Thus, the statistically significant increased frequencies of MN in vitro could be related to the lack of metabolic clearance of nimodipine by lymphocytes in culture, whereas in vivo the drug is readily metabolized. This may indicate that the cytogenetic effect of nimodipine is mainly due to the drug itself rather than its metabolites.
Different results in vivo and in vitro could be explained as well by the phenomenon of adaptive response to the drug in vivo. Wolff's work on the induction of chromosomal aberrations in human lymphocytes has shown that cells `adapted' with a low dose of radiation or chemical show much less damage after a subsequent exposure than was observed in cells not pre-exposed (adapted). The adaptive response can also be induced in vivo with low or chronic doses (Wolff, 1998). Thus, it could be that low and chronic doses of nimodipine in vivo induce mechanisms whereby cells became somewhat refractory to the induction of damage by subsequent exposure.
Further investigations focusing on the effect of nimodipine in vitro would be interesting. Possible demonstration of a dose-dependent response, use of relevant positive controls and use of an in vitro metabolizing system (S9 mix) would be useful before classification of this drug as an in vitro aneugen.
Different behaviours in vivo and in vitro have also been found with other compounds (Morimoto et al., 1993; Karacic et al., 1995; Awara et al., 1998; Wolff, 1998; Ahmad et al., 2000; Télez et al., 2000).
Aaron et al. (1993) and Vlastos and Stephanou (1998) reported that in vitro analysis alone is insufficient to identify hazardous effects and in vivo analyses also have to be carried out. Kramers et al. (1991) pointed out that negative in vivo results can overrule the finding of intrinsic mutagenic activity in vitro. According to Müller and Sofuni (2000) `nonrelevant positive results from in vitro systems are a common phenomenon in pharmacology and toxicology'. With regard to this, our results suggest that although an aneugenic effect could be attributed to nimodipine itself, chronic long-term therapy is not associated with increased genotoxicity in patients taking oral doses of nimodipine.
Previous studies on toxicology of nimodipine reported no evidence of mutagenic activity. Occasional malformations and an increase in mortality among offspring of pregnant animals occurred in initial studies but later studies showed no teratogenic or embryotoxic effects (Dollerf, 1991). However, toxicological data from animal experiments can only be used to a limited extent for human risk assessment because, as Aardema et al. (1998) pointed out, `to date, there is no information on the relevance of the data obtained in experimental animals for human beings and this is an area requiring further investigation'. Regarding this, our results in the study of nimodipine are interesting since they provide data on human beings exposed in vivo and in vitro to the drug which can be compared with those obtained from animal experiments.
These results support those reported by Andreassi et al. (1999), who evaluated the incidence of chromosome aberrations in human lymphocytes of patients with and without long-term exposure to six calcium antagonists (not including nimodipine), indicating a lack of association between calcium antagonist therapy and increased incidence of chromosomal damage.
The present study has revealed inter-individual variation in the frequency of all end-points studied.
The variability observed among patients may be associated with different factors, one being a particular individuals's responsiveness to the drug, but apparently not with differences in experimental protocols nor with age, sex, dose of nimodipine and/or duration of treatment.
As regards the inter-individual variation in control individuals, the differential response to nimodipine could be attributed to confounding factors such as sex and/or differences in genetic background among individuals that could influence metabolism of the compound, repair of DNA damage and also the percentage of cells that respond to the chemical. Different individual sensitivity is not surprising and significant inter-individual variations have been reported in the frequencies of SCE and MN following exposure to a large number of agents (Migliore et al., 1991; Grummt et al., 1993; Duffaud et al., 1997; Vlastos and Stephanou, 1998; Oliveira et al., 2000).
The spontaneous frequencies of SCE, MN and CN+ MN were in good agreement with those reported previously in the literature (Bolognesi et al., 1997; Migliore et al., 1997, 1999b). According to previous observations and the literature data (for example Zijno et al., 1996; Bolognesi et al., 1997; Fenech, 1998; Peace and Succop, 1999; Kirsch-Volders et al., 2000) a pronounced age-dependent increase in cytogenetic damage is found generally for MN. This effect could be explained by either accumulated genetic damage in lymphocytes (Eastmond and Tucker, 1989; Fenech, 1993) or a true aging process, such as altered cell metabolism and/or a decreased DNA repair capability (Fenech and Morley, 1986; Franceschi, 1989). Catalán et al. (1995) have attributed the significant increase in MN frequency with age to an aneuploidy phenomenon involving both autosomes and sex chromosomes. Our high MN frequencies can thus be attributed to the high age of the control sample. Chromosome loss is known to increase with increasing age and it is also known to be higher in females (Nowinski et al., 1990; Guttenbach et al., 1994; Stone and Sandberg, 1995). In our previous work (Télez et al., 2000) we found 48% CN+ MN in control individuals with an average age of 52.5 years, whereas in this present work 50.80% CN+ MN was found in a sample aged 70.8 years. According to this a positive correlation with age has not been found. The sex parameter showed no effect.
In summary, our results of the study of the genotoxic potential of nimodipine indicated that chronic long-term therapy with this compound is not associated with increased genotoxicity. In contrast, the ß-blocker antihypertensive drug atenolol showed aneugenic activity following in vivo treatment in humans (Télez et al., 2000). This could suggest that the genotoxic potential of a compound is related to the chemical class and/or mode of action. To elucidate this further investigations are needed focusing on antihypertensive drugs belonging to the same group.
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Acknowledgments |
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We thank Drs F.Barquinero and J.Surrallés for their technical help and great kindness. M.T. holds a doctoral fellowship from the University of the Basque Country. This study was supported by the Department of Education, Universities and Research of the Basque Government (PI96/85).
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Notes |
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4 To whom correspondence should be addressed. Tel: +34 94 601 5409; Fax: +34 94 464 8500; Email:ggbtesem{at}lg.ehu.es
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References |
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Received on November 15, 2000; accepted on April 4, 2001.
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