Biology of Reproduction, Vol 23, 324-330, Copyright © 1980 by Society for the Study of Reproduction

Reversal of Follicular Fluid Inhibition of Granulosa Cell Progesterone Secretion by Manipulation of Intracellular Cyclic AMP

¹ Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois 60115

Fluid from small (1-2 mm) porcine follicles inhibits progesterone secretion, LH stimulation of cyclic AMP (cAMP) accumulation, adenylyl cyclase activity and morphological luteinization of granulosa cells obtained from medium (3-5 mm) or large (6-12 mm) porcine follicles. The goal of the present experiments was to determine whether restoration of cAMP levels would reverse the inhibitory action of follicular fluid on progesterone secretion. Following 2-day incubations with either the inhibitory fluid from small follicles (SFFl) or noninhibitory fluid from large follicles (LFFl), the presence of phosphodiesterase inhibitors theophylline or 3-isobutylmethyl xanthine (MIX) restored LH stimulation of cAMP accumulation by SFFl-treated cells to 50% of that of the controls (i.e., LFFl-treated cells). LH and MIX together, but neither alone, fully restored progesterone secretion by SFF1-treated cells to amounts secreted by the controls. Analogs of cAMP, 8 bromo cyclic AMP (8 BrcAMP) and N²O⁶dibutyryl cyclic AMP (DBC), in combination with MIX, but not alone, also fully restored progesterone secretion by the inhibited cells. These data suggest that the follicular fluid does not alter the steroidogenic machinery of the granulosa cells directly, but influences it via inhibition of cAMP accumulation.

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ACKNOWLEDGMENTS The cAMP assays were done when the author was a postdoctoral fellow under the direction of Dr. C. P. Channing at the University of Pittsburgh, School of Medicine, Department of Physiology. The rest of the work was done at Northern Illinois University. Dr. Channing’s input in this portion of the work is gratefully acknowledged. I wish to thank Deborah Toth, Su Yu Ling and James Walsh for their technical assistance and Dr. B. W. Rigby for his discussions of the data.