Conversion of [4-14C]progesterone to androstenedione in vitro by thecal tissue from the ovary of the domestic fowl (Gallus domesticus).

The conversion of [4-14C]progesterone to androstenedione by thecal tissue homogenates from the large yellow follicles of the hen ovary was measured at two periods of the ovulatory cycle after incubation for 1 h in the presence of cofactors. Production of androstenedione by the largest follicle, F1, was reduced significantly 1-2 h before ovulation compared with 15 h before ovulation, whereas production of an unidentified androgen increased. These differences were not observed in the next largest follicles, F2 and F3. Thecal tissue homogenates from all the follicles converted [4-14C]progesterone to 17 alpha-hydroxyprogesterone, androstenedione and testosterone.