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 was studied in guinea-pig seminal vesicles. The nitric oxide synthase (NOS) activity was estimated and reduced nicotinamide-adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry was performed. Furthermore, 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 inhibitorsNG-nitrol-arginine methyl ester (L-NAME) andNG-nitrol-ar-ginine (L-NNA) inhibited carbachol-induced fructose secretion but the D-isomer to L-NAME had no effect. Whenl-arginine was administered together with L-NAME, no inhibitory effect on the carbachol-induced fructose secretion could be seen. Nerve-induced fructose secretion was also inhibited by L-NAME. The NO donor glyceryl trinitrate (GTN) increased the fructose secretion. Carbachol or GTN did not increase cGMP levels, nor was fructose secretion inhibited by a guanylate cyclase inhibitor (ODQ). Our results suggests that glandular NO production is a prerequisite for muscarinic fructose secretion in the seminal vesicle via a cGMP-independent pathway.