[Chromosome analysis of female baboons following treatment with STS 557 and levonorgestrel].

Adult, female baboons (Papio hamadryas) were administered orally once 18 h p.c., either 1.6 mg STS 557 (17 alpha-cyanomethyl-17 beta-hydroxy-estra-4;9(10)-dien-3-one) or 1.6 mg levonorgestrel. Investigations of the bone-marrow cells of these animals showed, compared to untreated controls, no signs of increased chromosome aberrations caused by the substances. The relative frequency of chromosome aberrations were estimated for controls: STS 557: levonorgestrel with 0.60 +/- 0.35 : 0.55 +/- 0.39 : 0.92 +/- 0.46%, respectively. The differences between the three groups investigated in the exact Fisher-test (2 alpha = 0.05) were not significant.