IncreasedInductionof Sister ChromatidExchangeby Diethyistilbestrol in Lymphocytes from Pregnant and Premenopausal Women1

Cultures of whole blood from pregnant women (4 to 6 months), premenopausal women, postmenopausal women, and normal men were grown in the presence of varying concentra tions (1 x 1o-@M, 2 x 1O@M, and 4 x 1O'@M) of diethylstil bestrol (DES), a synthetic estrogen and known carcinogen, to see if It had sex-related cytogenetic effects. DES induced sister chromatid exchanges in lymphocytes from pregnant and pre menopausal women but had only a small effect at the highest concentration (4 x 1o@ M) in lymphocytes from men and postmenopausal women. At all concentrations, the average number of sister chromatid exchanges was higher in lympho cytes from pregnant women than in those from premenopausal women. In lymphocytes from both a man and a pregnant woman, DES strongly inhibited cell proliferation in vitro. When lymphocytes from a man and a pregnant woman were cocul tured in the presence of DES, only the lymphocytes of the woman responded with an increase in sister chromatid ex changes. This indicated that there is no interaction between DES and a factor present in the blood but that DES acts directly