Interaction of Granulosa and Theca Layers in the Control of Progesterone Secretion in the Domestic Hen12

The ovulatory cycle of the domestic hen is approximately 26 h in length. The hen ovulates an egg each day at a progressively later time until she finally skips a day, resets her “clock” and a new sequence is started. The ovarian component of this unique timing mechanism is the focus of this report. In Experiment 1, we asked whether there was a difference in luteinizing hormone (LH)-stimulated progesterone (P4) secretion by the granulosa layer removed from the largest follicle (F1) that had been the F1 follicle for 8, 12, or 32 h. In Experiment 2, our objective was to determine whether the theca layer of an F1 follicle influenced P4 secretion by the granulosa layer of that follicle and whether such an interaction depended on the maturity of the F1 follicle (had been a F1 follicle for 8 h or 32 h). Results from Experiment 1 revealed that there was no significant difference in LH-stimulated P4 secretion by the granulosa layer in a perifusion system regardless of the length of time the follicle had been the largest follicle. In contrast, in Experiment 2, when granulosa and theca layers from the same follicle were co-incubated in a perifusion system, P4 secretion from the more mature F1 follicle (32 h) increased in response to LH, whereas P4 secretion from the less mature F1 follicle (8 h) was not elevated by LH. We attributed this unique response to a specific effect of the theca layer on the granulosa layer because the control tissue (muscle) did not alter the pattern of P4 secretion by the granulosa layer of either the less mature or the more mature F1 follicle. Whereas testosterone (T) secretion from the less mature F1 follicle (8 h) increased in response to LH, T secretion from the more mature F1 follicle (32 h) was undetectable and not LH responsive. Finally, estradiol (E2) secretion from the more mature F1 follicle (32 h) was significantly lower than that from the less mature F1 follicle (8 h), while E2 secretion decreased for both follicles during the sampling time. Finally, T and E2 secretion were not different whether the theca layer was incubated alone or co-incubated with the granulosa layer. We conclude that the interaction of the theca and granulosa layers may bean important mechanism in modulating follicular responsiveness to LH.