Renal actions of dendroaspis natriuretic peptide in rabbits

Dendroaspis natriuretic peptide (DNP) is one of four members of the natriuretic peptide family sharing functional and structural properties. The purpose of the present study was to elucidate the physiological role of DNP on renal functions and its cellular mechanism in the rabbit kidney. DNP (5 μg/kg/min) infused intravenously increased urine volume and urinary excretion of electrolytes. These renal actions induced by DNP were more pronounced than those caused by atrial natriuretic peptide (ANP). We compared profiles of ¹²⁵I-ANP and ¹²⁵I-DNP by reverse-phase HPLC during incubation in rabbit plasma at 37 °C for 1, 2, and 4 h. While ¹²⁵I-ANP was quickly degraded within 1 h, ¹²⁵I-DNP was still stable in plasma for 4 h. DNP induced the greatest cyclic guanosine monophosphate (cGMP) production in the glomeruli in a dose-dependent manner, when compared to other renal structures including cortical tubules, outer medullary tubules, and inner medullary tubules. Affinity cross-linking analysis revealed NPR-A is selective receptor for DNP in glomeruli. Forskolin, a stimulator of adenylyl cyclase, significantly decreased cGMP production in the renal glomeruli but not in the renal medulla. In summary, DNP is a more effective activator of renal functions than ANP, possibly because of the degradation resistance of DNP against the endogenous peptidases in plasma or tissues. These findings suggest that DNP plays a pivotal role as a renal regulating peptide via specific natriuretic peptide receptors with a guanylyl cyclase domain.