SEVERAL ISOFORMS OF NITRIC-OXIDE (NO) SYNTHASE ARE PRESENT IN THE RATOVIDUCT

We have studied the possible existence of NO synthase in rat oviducts, using differents methodologies. Measurement of the conversion of L-[C -14]arginine into L-[C-14]citrulline demonstrated the presence of a si gnificant NO synthase activity that could be inhibited by N-monomethyl -L-arginine (L-NMMA), N-L-arginine-methyl-ester (L-NAME), aminoguanidi ne (AG), methylene blue (MB) and EGTA. The inhibition pattern suggeste d that both Ca2+ dependent (or constitutive) and Ca2+ independent (or inducible) NO synthase isoforms were present in the rat oviduct. This was confirmed by SDS-PAGE and Western blotting of oviductal homogenate s, where mio different bands could be recognized. A 155 kDa band was d etected by a serum against neuronal NO synthase, whereas a 120 kDa was detected by a serum against macrophage NO synthase. Immunohistochemis try revealed the presence of neuronal NO synthase in a sparse populati on of nerves fibers mainly confined to the medial third of the oviduct . Epithelial cells contained the largest deposits of immunoreactivity. All antisera, whether directed to neuronal or inducible NO synthases, gave a strong reaction in subpopulation of epithelial cells, usually appearing in clusters. These cells also exhibited a strong NADPH diaph orase activity and were much more numerous towards the fimbrial end of the tube.