Inhibition of endogenous nitric oxide synthesis activates particulate guanylyl cyclase in the rat renal glomeruli

Nitric oxide (NO) plays a crucial role in the regulation of kidney function and metabolism. Our previous study showed that dexamethasone, one of several known selective inhibitors of inducible nitric oxide synthase (NOS), had a stimulatory effect on soluble guanylyl cyclase in the glomeruli of rat kidney. However, in the presence of dexamethasone, the atrial natriuretic factor (ANF)-dependent system remained suppressed. The aim of the present study was to investigate whether inhibition of synthesis of endogenous NO modulates the activity of the guanylyl cyclase system(s) in glomeruli. In these studies, rats were injected with a non-selective NOS inhibitor, N-omega-nitro-L-arginine methyl ester (NAME; NAME-group), or saline solution (controls; C-group). Creatinine clearance (C(Cr)), and plasma and urinary nitrate/nitrite (NOx-) levels decreased in the NAME-group, but plasma and urinary guanosine 3',5'-cyclic monophosphate (cGMP) contents were unchanged. In the presence of 0.1 microM ANF, synthesis of cGMP in the NAME-group exceeded threefold the cGMP production in the C-group. In addition, the pre-contracted glomeruli of the NAME-group were fully relaxed at 0.1 microM ANF, but glomeruli obtained from the C-group were relaxed in the presence of a 10 times higher dose of ANF. The increased sensitivity of glomeruli to ANF was possibly due to the more than doubled activity of particulate guanylyl cyclase (pGC) in the NAME-group in comparison with the C-group. In the presence of 100 microM sodium nitroprusside (SNP), soluble guanylyl cyclase (sGC) generated significantly lower cGMP production in the NAME-group than in the C-group (1.61 +/- 0.33 vs. 2.91 +/- 0.69 nmol/mg protein/10 min, respectively). These results demonstrate that inhibition of the synthesis of endogenous NO may also have an inhibitory effect on the activity of sGC. In addition, increased activity of the pGC and ANF-dependent system appears to be compensatory to the altered activity of soluble guanylyl cyclase.