In vitro effect of danazol on luteinizing hormone-releasing hormone-stimulated luteinizing hormone release in rat anterior pituitary cell cultures in vitro.

Monolayer cultures of anterior pituitary glands from female rats were exposed to 5 X 10(-6) M danazol for 0, 4, 24, 48, and 72 h in Dulbecco's Modified Eagle's Medium supplemented with 10% horse serum and 2.5% fetal calf serum. After this treatment, the cell cultures were rinsed and challenged with 10(-8) M LHRH for 6 h. The media were collected and assayed for LH by a hormone-specific RIA using the double antibody precipitation technique. A control incubation was carried out by exposing cell cultures for the same length of time in the absence of danazol but in the presence of 0.5% ethanol in which danazol was dissolved, then challenging the culture with 10(-8) M LHRH, as was done in the experimental group, and assaying the LH released in the medium. The results showed that exposure of cell cultures to danazol caused a significant decrease in LH release in response to LHRH from 13,800 +/- 500 to 3,500 +/- 200 ng/ml. The inhibition of LH release was dependent on both the duration of danazol exposure and its concentration. Danazol exposure had, however, little effect on basal LH secretion by the pituitaries, which remained at about 600 ng/ml at all time points examined. Under the experimental conditions, danazol exerted no effect on the incorporation of amino acid into protein in the cell culture. These results suggest that one of the mechanisms of the antigonadotropic effect of danazol is inhibition of the responsiveness of the pituitary to LHRH-induced LH release.