Biosynthesis of nitric oxide and citrulline from L-arginine by constitutive nitric oxide synthase present in rabbit corpus cavernosum.

摘要: Summary The objective of this study was to determine whether a constitutive isoform nitric oxide (NO) synthase is present in rabbit corpus cavernosum that could account for the involvement L-arginine-NO pathway neurogenically-elicited relaxation and, therefore, penile erection. Citrulline determined by monitoring formation 3 H-citrulline from H-L-arginine. NO total X (NO + nitrite [NO 2 − ] nitrate[NO ]) chemiluminescence after reduction acidic vanadium (III). Equimolar quantities plus citrulline were generated L-arginine and both products time-dependent at 37°C. activity distributed almost entirely cytosolic fraction. Enzymatic completely dependent on NADPH, calmodulin, calcium. Addition tetrahydrobiopterin increased about 30 percent. inhibitor N G -nitro-L-arginine, abolished enzymatic activity. Km 17 μ M Vmax reaction 18 pmol/min/ mg protein. These observations indicate cytosolic, synthase, like found brain neuronal tissue, cavernosum.