Nitric oxide synthesis inhibition promotes renal production of carbon monoxide

We tested the hypothesis that the status of NO synthesis influences the renal heme-heme oxygenase system. Studies were conducted in untreated rats and rats treated with the NO synthesis inhibitor N G -nitro- l -arginine methyl ester for 2 days. Treated and untreated rats were contrasted in terms of renal expression of heme oxygenase-1 and -2, renal carbon monoxide (CO)-generating activity, and urinary CO concentration and excretion rate. Heme oxygenase-1 and -2 proteins were similarly expressed in the kidneys of untreated and treated rats. In contrast, the NADPH-dependent component of the CO-generating activity of renal homogenates incubated with heme (a measure of heme oxygenase activity) was higher ( P P