Homologous and heterologous desensitization of a guanylyl cyclase-linked nitric oxide receptor in cultured rat medullary interstitial cells

Selected studies of nitroglycerin tolerance have demonstrated desensitization of the nitric oxide-stimulated guanylyl cyclase. To define the mechanism by which the response to nitric oxide becomes desensitized, we studied the effects of activating both nitric oxide and atrial natriuretic peptide-stimulated guanylyl cyclases in rat medullary interstitial cells. Cells were pretreated with the nitric oxide agonists nitroprusside (SNP) and SIN-1 for 18 hr before measuring SNP- or SIN-1-stimulated cyclic GMP (cGMP) accumulation in the presence of 3-isobutyl-1-methylxanthine. Pretreatment with SNP decreased SNP- and SIN-1-stimulated cGMP accumulation without altering the EC₅₀ for SNP. Pretreatment with SIN-1 also inhibited SNP and SIN-1-stimulated cGMP accumulation. To rule out a nonspecific metabolic effect of SNP, we showed that SNP pretreatment decreased SIN-1-stimulated soluble guanylyl cyclase activity, but had no significant effect on forskolin-stimulated cyclic AMP accumulation. Pretreatment with SNP also decreased the mRNA abundance of the α₁- and β₁-subunits of guanylyl cyclase. Pretreatment with either atrial natriuretic peptide or 8- chlorophenylthio-cGMP inhibited SNP-stimulated cGMP. We conclude that the soluble guanylyl cyclase-linked nitric oxide receptor exhibits homologous and heterologous desensitization in rat medullary interstitial cells. The site of regulation is unknown, but homologous desensitization may involve decreased abundance of soluble guanylyl cyclase.