| Abstract: | Collagenase-dispersed theca cells from the 3rd and 4th largest ovarian follicles (T3) were responsive to LH stimulation of both oestrogen and androstenedione production, whereas theca cells from the largest follicle (T1) failed to respond to the gonadotrophin stimulation. Similarly, 8-bromo cAMP and forskolin were more effective in stimulating oestrogen and androstenedione production in T3 than in T1 cells, indicating that post-receptor events were involved in the decreased LH responsiveness of T1 cells. The C17-20-lyase activity, as measured by conversion of [3H]17-hydroxyprogesterone to androstenedione, was greatly reduced in T1 cells as compared to T3 cells. The results demonstrate that a decrease in C17-20-lyase activity, in addition to a decrease in aromatase activity, contributes to the loss of LH-stimulated steroidogenesis in mature theca cells. |
