LH-Stimulable Adenylyl Cyclase Activity During the Ovulatory Cycle in Granulosa Cells of the Three Largest Follicles and the Postovulatory Follicle of the Domestic Hen (Gallus domesticus)

The adenylyl cyclase (AC) activity in the granulosa (Gr) cells of the largest (F1), next largest (F2), third largest (F3), and postovulatory (POF) follicles throughout the ovulatory cycle of the domestic hen was measured. Granulosa cells were isolated at 24, 18, 12, 8, 6, 4, and 2 h before ovulation and basal and LH-stimulable AC activities were determined. There was a significant difference (P<0.05) in response between the basal and LH-stimulable activities of the F1 Gr at all times studied, with the most dramatic difference observed between 18 and 12 h before ovulation (P<0.001) (18 h, 58.42 ± 4.72 vs 12 h, 105.13 ± 4.89 pmoles cAMP/min/mg protein). There was a transient decrease in basal and LH-stimulable AC activities after the LH surge, followed by a significant (P<0.05) increase in basal activity 2 h before ovulation (6 h, 34.55 ± 3.94 vs 2 h, 53.76 ± 4.35 pmoles cAMP/min/mg protein). The fluctuations in basal and LH-stimulable AC activities of the F2 Gr cells were essentially the same as those of the F1 Gr except that the relative LH stimulation was less. In contrast, the pattern of AC activity of the F3 Gr cells differed from that of the F1 and F2 follicles. At all times assayed except 6 and 4 h before ovulation, the LH-stimulable activity was significantly greater (P<0.05) than basal values, which remained the same throughout the cycle. The LH-stimulable AC activity of the Gr cells of the POF was still significantly (P<0.001) elevated 2 h after ovulation, but declined to basal levels 4 h later. There was a significant increase in the basal AC activity of the POF at 24 h after ovulation. These results demonstrate that there is an increase in the cAMP synthesizing capacity of the Gr cells of preovulatory follicles as they approach ovulation. The loss of LH-stimulable AC activity in the POF Cr cells may be due to gonadotropin desensitization or cell death.