Small intestine as possible source of increased plasma cGMP after administration of alpha-hANP to dogs.

A synthetic alpha-human atrial natriuretic peptide (alpha-hANP) was infused into the renal artery of anesthetized dogs, and the urine flow, renal hemodynamics, and plasma guanosine 3',5'-cyclic monophosphate (cGMP) were determined. alpha-hANP led to a natriuresis accompanied by an increase in renal blood flow in the infused kidney but not in the contralateral kidney. The systemic blood pressure remained unchanged. The arterial plasma cGMP significantly increased after alpha-hANP administration. The plasma cGMP in the renal vein was significantly lower than that in the aorta throughout the experiment; therefore the elevated circulating cGMP was probably of extrarenal origin. The plasma cGMP in the right ventricle and femoral vein was also increased to the same extent seen in the aorta. On the other hand, plasma cGMP in the superior mesenteric vein was remarkably increased over that in the aorta. After the administration of alpha-hANP, the increased circulating cGMP seems to be the result of an enhancement of production of this nucleotide from the small intestine or organs drained by the superior mesenteric venous circulation.