Effects of organochlorine pesticides on DNA synthesis of cultured oviductal and uterine cells and on estrogen receptor of uterine tissue from heifers.

The pesticides DDT, MXC and gamma HCH at concentrations between 41 and 200 microM inhibited DNA synthesis (measured by [3H]thymidine incorporation) of cultured bovine oviductal endosalpingeal and uterine cells in the order DDT > MXC > gamma HCH, in comparison ton nonexposed controls. Sensitivity to the toxicants was greater in uterine epithelial and stromal cells than in uterine smooth muscle or oviductal endosalpingeal cells. Besides the inhibitory effect, there was a stimulatory effect on DNA synthesis in epithelial cells in the range of 28 nM to 2.8 microM DDT and in stromal cells at 2.8 and 28 nM for MXC. An explanation for this reaction could be that both toxicants have an estrogen-like effect. In the present study, it is shown that the o,p' isomer of DDT can bind to the cytoplasmatic estrogen receptor and DDT or MXC were able to inhibit the binding of radiolabelled estradiol to the uterine endometrial explants in bovine, whereas gamma HCH did not change the binding. These findings represent an estrogenic effect of DDT and MXC in two complete in vitro systems.