STIMULATION OF NITRIC OXIDE-CYCLIC GUANOSINE-MONOPHOSPHATE PATHWAY INBOVINE OVARIAN THECA CELLS BY TUMOR-NECROSIS-FACTOR-ALPHA (TNF-ALPHA)- IS THIS PATHWAY IMPLICATED IN THE TNF-ALPHA-INDUCED INHIBITION OF LUTEINIZING HORMONE-STIMULATED PRORENIN PRODUCTION

Gonadal functions is known to be controlled by many factors, including locally acting cytokines like tumor necrosis factor alpha (TNF alpha) . One of the ways this cytokine acts is via the nitric oxide (NO)-cGMP pathway. Since we have shown that in the ovary theca cells are a targ et of TNF alpha's action, it was of interest to determine whether such a mechanism can be implicated in the observed TNF alpha-mediated of L H-stimulated prorenin synthesis and secretion. Treatments of isolated theca cells with TNF alpha resulted in a dose- and time-dependent incr ease in cGMP production. This increase was not detectable until 6 h af ter the addition of TNF alpha and was totally abolished by the protein synthesis inhibitor cycloheximide. Addition of either L-N-6-nitroargi nine methyl ester (L-NAME), an inhibitor of all three NO synthase (NOS ) isoforms, or 2-amino-5,6-dihydro-methyl-4H,1,3-thiazine (AMT), a spe cific inhibitor of the inducible isoform of the inducible isoform of t he enzyme, likewise reversed the action of TNF alpha on cGMP formation . Finally, addition of 1H-[1,2,4]oxadiazole [4,3-a] quinoxalin 1-one ( ODQ), an inhibitor of NO-sensitive soluble guanylate cyclase, resulted in a concentration-dependent reduction of TNF alpha-stimulated cGMP f ormation. In contrast, the TNF alpha-mediated inhibition of LH-stimula ted prorenin secretion was not affected by either L-NAME AMT, or ODQ. Also the addition of stimulators of soluble guanylate cyclase, sodium nitroprusside, and S-nitroso-N-acetylpenicillamine, or 8 bromo-cGMP ha d no effect on the action of LH on theca cells. We conclude that altho ugh TNF alpha is able to stimulate cGMP formation in theca cells by in ducing the expression of inducible NOS, the mechanism underlying the T NF alpha-mediated inhibition of LH-stimulated prorenin production is i ndependent of its ability to induce cGMP formation.