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.