Co-operation between particulate and soluble guanylyl cyclase systems in the rat renal glomeruli

ANP and NO act via different receptors, although inducing the common intracellular messenger - cyclic GMP. However, interaction between both factors remains unclear. Our observations suggested that in the rat kidney glomeruli, activities of the ANP- and NO-dependent guanylyl cyclase systems may be mutually compensated. To check this, we have tested effects of ANP and sodium nitroprusside (SNP) on cGMP synthesis and relaxation of glomeruli contracted with angiotensin II. The glomeruli were isolated from Wistar rats receiving saline (Control), dexamethasone (DEX), deoxycorticosterone (DOCA) or N-omega-nitro-L-arginine methyl ester (NAME) for 1 or 2 days. In the DEX glomeruli exposed to 100 mu M SNP, rate of cGMP synthesis was significantly higher then in the Control (26.3 vs 16.0 pmol/mg.prot./2min., P < 0.05), while 1 mu M ANP was markedly less effective (2.8 vs 16.7 pmol/mg.prot./2min in Control, P < 0.01). On the contrary, in NAME group 1 mu M ANP stimulated cGMP synthesis up to 35.6 pmol/mg.prot./2min whereas efficacy of SNP was slightly suppressed. High correlation coefficient (r = 0.979, p < 0.01) indicates interrelationship between NO- and ANP-dependent cGMP synthesis. Ability of the glomeruli to relax in response to ANP or SNP was in accord to their ability to cGMP generation. This was confirmed by high correlation (r = 0.845, p < 0.001) between degree of relaxation and rate of cGMP synthesis. Our results support strongly the hypothesis that both, ANP and NO dependent systems co-operate in regulation of the function of kidney glomeruli.