Further investigations on the cytological effects of some contraceptives

Effect of a low-dose ethinylestradiol and gestodene in combination on the frequency of micronuclei in human peripheral blood lymphocytes of healthy women in vivo

BACKGROUND

Since most oral hormonal contraceptives contain a fixed combination of ethinylestradiol and gestodene as an estrogenic/progestogenic component, we decided to evaluate the possible mutagenic effect of a low-dose contraceptive pills containing 20 microg ethinylestradiol and 75 microg gestodene.

METHODS

A total of 30 healthy women received hormonal contraception during six consecutive menstrual cycles. A single daily dose was 20 microg ethinylestradiol and 75 microg gestodene. The pills were taken orally in a monthly cycle of 3 weeks on and 1 week off. In the investigation of the mutagenic effect of these contraceptive pills in vivo, the cytokinesis block micronucleus (CBMN) test was used, and the frequency of micronuclei (MN) in peripheral blood lymphocytes was determined.

RESULTS

Average MN frequency in women before therapy was 7.40 +/- 0.75 MN/1000 analyzed cells, and after therapy was 7.37 +/- 0.59 MN/1000 analyzed cells (p > 0.05).

CONCLUSION

Our data suggest that oral contraception with 20 microg ethinylestradiol and 75 microg gestodene in combination during six consecutive menstrual cycles does not induce micronuclei in peripheral blood lymphocytes of women.

Pharmacology and toxicology of ethinyl estradiol and norethindrone acetate in experimental animals

For over 30 years various combinations of synthetic estrogens and progestins have been used in oral contraceptive formulations. Ethinyl estradiol (EE) and norethindrone acetate (NA) are common synthetic hormones used in oral contraceptives such as Loestrin, Brevicon, Ortho-Novum, Norlestrin, and Norinyl. In recent years these oral contraceptives have been considered for development in other therapeutic indications. Given the use of these agents for other clinical indications with different and larger target populations, an updated comprehensive review of the toxicology literature of estrogens and progestins is warranted. This review will summarize available data on the pharmacology and toxicology of estrogens and progestins with an emphasis on the specific synthetic hormones EE and NA. Ethinyl estradiol and norethindrone acetate alone or in combination, possess low acute and chronic toxicity. In some studies, EE and/or NA increased the incidence of specific tumors in susceptible strains of rodents and dogs, but not monkeys. These agents are not teratogenic when given in combination. Alone EE and NA have clastogenic properties. Overall, the animal data demonstrates that long-term exposure to EE and NA formulations pose very little health risks to humans.

Evaluation of genotoxic potential of synthetic progestins-norethindrone and norgestrel in human lymphocytes in vitro

The genotoxicity study of two widely used contraceptive synthetic progestins, i.e. norgestrel and norethindrone was carried out on human lymphocyte chromosomes using chromosomal aberrations (CA), sister chromatid exchanges (SCE) and cell growth kinetics as parameters. The study was carried out both in the presence as well as in the absence of metabolic activation (S(9) mix). The lymphocytes were exposed to three different concentrations of the drugs (20, 40 and 75 microg/ml for norethindrone and 10, 25 and 50 microg/ml for norgestrel) for three different durations (24, 48 and 72 h). The drug norethindrone was found to be non-genotoxic at any concentration and at any exposure duration either in the presence or in the absence of S(9) mix. But another drug norgestrel was found to affect the genetic material. It induces CA, SCE at significant level, and inhibits lymphocyte proliferation at 25 and 50 microg/ml of concentrations only. In the presence of S(9) mix the values obtained for CA, SCE and mitotic index (MI) were more significant. A time and dose relationship was also observed. It was concluded that norgestrel itself and possibly its metabolites are potent mutagens beyond a particular dose in human lymphocytes.

17-alpha-ethinylestradiol and norgestrel in combination induce micronucleus increases and aneuploidy in human lymphocyte and fibroblast cultures

Oral contraceptives are highly efficient and easily administered drugs; however, it must not be forgotten that they are composed of chemical substances which can be classified as potential carcinogens. Testing of a substance for genotoxicity represents a reliable approach both to evaluate the genetic hazard and to obtain information on its possible tumorigenic (cancerogenic) properties. The present study was undertaken to evaluate through carefully planned and controlled investigations the in vitro cytogenetic effects of oral contraceptives (ethynilestradiol and norgestrel mixed in the proportion 1:5) using three different concentrations, with two different durations of treatment (48 and 72 h), on two types of human cells (lymphocytes and fibroblasts) and a series of short-term test procedures: sister chromatid exchange (SCE), micronucleus test (MN), and chromosome aberrations (CA). In addition, the FISH procedure and in vitro anaphase and metaphase preparation analyses were performed. In contrast to CA and SCE frequencies, the frequency of MN in treated blood lymphocytes showed higher values by comparison with the controls, although the difference was statistically significant only for the lowest concentration (P = 0. 016). When using pancentromeric alphoid probes, the FISH procedure gave positive signals in more than 85% of micronuclei, clearly indicating that MN may contain whole chromosomes rather than acentric fragments. Unlike the lymphocytes, the fibroblasts showed dose-dependent effects, although those treated with the highest hormone concentrations showed an increased number of highly damaged cells (cytoplasmatic vacuolization, nuclear fragmentation, etc.), a decreased number of anaphase cells, a large number of which were abnormal, and a reduction of mitotic index. In conclusion, our data confirm that hormones do not induce structural chromosome aberrations in lymphocytes and indicate that ethynilestradiol and norgestrel have an aneugenic effect on fibroblast and lymphocyte cultures; FISH analysis on micronuclei from lymphocyte cultures and anaphase preparations from fibroblast cultures support this hypothesis. Teratogenesis Carcinog. Mutagen. 20:147-159, 2000.

Genotoxic effects of estradiol-17beta on human lymphocyte chromosomes

The cytogenetic effect of a hormonal steroid, estradiol-17beta, was assessed in peripheral blood human lymphocyte culture. Sister chromatid exchanges (SCE) and chromosome aberrations (CA) were scored as genetic end points. Significant induction of CA was observed at 25 microg/ml and 50 microg/ml concentrations of estradiol-17beta in the absence of microsomal activation. The drug was effective in all treatments in the presence of rat liver S(9) microsomal fraction (S(9) mix) and exhibited increased frequency of chromosomal aberrations. The drug was effective in increasing the SCE frequency which was found to be maximum at the dose of 50 microg/ml concentration (i.e., 4.34+/-1.22) both with and without metabolic activation. It was found that estradiol-17beta itself and possibly its metabolites are potent mutagens beyond a particular dose in human lymphocytes.

Genotoxicity of lynoral (ethinyloestradiol, an oestrogen) in mouse bone marrow cells, in vivo

The genotoxic effect of Lynoral (ethinyloestradiol, an oestrogen) was studied using mouse bone marrow cells treated in vivo, employing a chromosomal aberration assay and micronucleus test. The dose and time-yield effects of the sex hormonal drug were investigated. Lynoral failed to induce significant genetic damage in the bone marrow erythrocytes of mice, regarding chromosomal aberrations and micronuclei.

Studies on the genotoxicity of tamoxifen citrate in mouse bone marrow cells

The genotoxic effects of tamoxifen citrate, an anti-oestrogenic drug, were studied using mouse bone marrow chromosome aberration assay (CA) and micronucleus (MN) test. The dose and time yield effects of the drug were investigated after repeated administration of various doses of the drug for 10 days. The doses used were, 0.1, 0.2, 0.4 and 0.8 mg/kg/day. Bone marrow preparations were made at 24, 48, 72 and 96 h after the last administration. The anticancer drug cyclophosphamide (CP) at a dose of 100 mg/kg was used as positive control. A statistically significant chromosomal aberration and MN induced by tamoxifen revealed its clastogenic potency.

Progestin (norethisterone)-induced genetic damage in mouse bone marrow

Primolut-N tablets containing norethisterone were assessed for their in vivo genotoxic effect on the bone marrow cells of Swiss albino mice. The chromosomal aberration assay and the micronucleus test were employed for the study. Statistically significant increases in chromosomal aberrations were induced by doses > or = 3.0 mg/kg/day. The maximum frequency of aberrations was induced at 24 h, thereafter decreasing with increasing time. But the drug Primolut-N did not induce a significant increase in the number of micronuclei in bone marrow erythrocytes at any of the doses and time intervals studied.

Genotoxic effect of Anovlar 21, an oral contraceptive, on mouse bone marrow

Anovlar 21, a combination drug containing the oestrogen ethinyloestradiol and the progestin norethisterone acetate, was studied for its in vivo genotoxic effect on the bone marrow cells of Swiss albino mice. The chromosomal aberration assay and the micronucleus test were employed for the study. 0.08, 0.4, 0.8, 1.6, 3.2, 4.8, 6.4 and 8.0 mg/kg/day of the drug was orally administered for 15 consecutive days to mice. Bone marrow preparations were made 24 h after the final feeding. The lowest dose, 0.08 mg/kg, represents the human therapeutic range. Marrow preparations of mice fed 0.8 mg/kg/day for 15 days were made at 6, 12, 24, 48 and 96 h, and 1, 2 and 3 weeks and a time-yield analysis was carried out. Statistically significant increases in chromosomal aberrations were observed in animal groups fed doses of greater than or equal to 0.4 mg/kg/day. In the time-response study, the maximum frequency of aberrations was noted at 24 h, thereafter decreasing gradually with increasing time. But the drug did not induce a significant increase in the number of micronuclei in bone marrow erythrocytes at any of the doses or time intervals studied.