IS GLANDULAR FORMATION OF NITRIC-OXIDE A PREREQUISITE FOR MUSCARINIC SECRETION OF FRUCTOSE IN THE GUINEA-PIG SEMINAL-VESICLE

The significance of nitric oxide (NO) formation in seminal secretion w as studied in guinea-pig seminal vesicles. The nitric oxide synthase ( NOS) activity was estimated and reduced nicotinamide-adenine dinucleot ide phosphate (NADPH)-diaphorase histochemistry was performed. Further more, cyclic guanosine 3,5-monophosphate (cGMP) concentration as well as fructose secretion from isolated vesicles was estimated. High Ca2+- dependent NOS activity as well as prominent glandular NADPH-diaphorase staining was found in the secretory epithelium. The NOS inhibitors N- G-nitro L-arginine methyl ester (L-NAME) and N-G-nitro L-arginine (L-N NA) inhibited carbachol-induced fructose secretion but the D-isomer to L-NAME had no effect. When L-arginine was administered together with L-NAME, no inhibitory effect on the carbachol-induced fructose secreti on could be seen. Nerve-induced fructose secretion was also inhibited by L-NAME. The NO donor glyceryl trinitrate (GTN) increased the fructo se secretion. Carbachol or GTN did not increase cGMP levels, nor was f ructose secretion inhibited by a guanylate cyclase inhibitor (ODQ). Ou r results suggests that glandular NO production is a prerequisite for muscarinic fructose secretion in the seminal vesicle via a cGMP-indepe ndent pathway.