Interleukin 1: an inhibitor of luteinizing hormone receptor formation in cultured rat granulosa cells

We have shown that interleukin 1 (IL 1) suppresses follicle-stimulating hormone (FSH)-induced progesterone secretion and 125I-labeled human chorionic gonadotropin (hCG) binding (a measurement of LH receptors) in cultured rat granulosa cells. The present study was designed to examine if the reduction of FSH-stimulated 125I-labeled hCG binding by IL 1 was caused by a decline in the binding capacity or by an alteration in the affinity of the LH receptor and, further, to determine the minimum period of exposure of the granulosa cells to IL 1 necessary to suppress 125I-labeled hCG binding. IL 1 produced a dose-dependent inhibition of 125I-labeled hCG binding in FSH-stimulated granulosa cells. Scatchard analysis revealed that this effect resulted from a reduction of the binding capacity of the LH receptor with no change in affinity. Also, a minimum of 12-24 h of exposure to IL 1 is necessary to significantly inhibit FSH-induced LH receptor formation. These results suggest that IL 1 decreases the number of LH receptors and that protein synthesis may be necessary for IL 1's action. However, a physiological/pathological role for IL 1 in ovarian regulation has yet to be established.