Permissive role of dopamine in renal action of ANP in volume-expanded rats.

A possible role of dopamine in the diuretic and natriuretic action of atrial natriuretic peptide (ANP) was evaluated in the rat. ANP was infused into the left renal artery of anesthetized rats whose kidneys were denervated. ANP both at 12 and 1.2 pmol/h caused immediate ipsilateral increases in urine volume (V), urine Na excretion (UNaV), and fractional excretion of Na (FENa). Ipsilateral glomerular filtration rate (GFR) and renal plasma flow (RPF) increased with 12 pmol/h ANP but not with 1.2 pmol/h ANP. Intravenous infusion of haloperidol, Sch-23390, or carbidopa markedly attenuated the increase in V, UNaV, and FENa with 12 pmol/h ANP and completely abolished the increases in GFR and RPF. Haloperidol, Sch-23390, and carbidopa also completely abolished the renal effects of 1.2 pmol/h ANP. In the presence of carbidopa, a small dose of dopamine infused into the systemic circulation, which by itself has no effects on blood pressure, V, GFR, RPF, and UNaV, restored the diuretic and natriuretic effects of ANP. In addition, an increase in urinary guanosine 3',5'-cyclic monophosphate by ANP was not affected by either haloperidol or carbidopa. These data indicate that dopamine may be necessary, as a permissive agent, for the renal effects of ANP to manifest and that the effects of dopamine may be independent of ANP-stimulated guanylate cyclase activation.