Intrarenal atrial natriuretic peptide infusion lowers arterial pressure chronically

Chronic intravenous infusions of atrial natriuretic peptide (ANP) have been shown to lower mean arterial pressure (MAP) in both normal and hypertensive animals. However, the importance of the renal actions of ANP in mediating this hypotension is unknown. This study was designed to determine whether physiological or pathophysiological increases in intrarenal ANP levels influence long-term control of arterial pressure. ANP was infused into the renal artery of seven conscious, uninephrectomized, chronically instrumented dogs at 1, 2, and 4 ng.kg-1.min-1 for 7 days at each dose, followed by a recovery period. Then ANP was infused intravenously following the same protocol. MAP decreased from 88 +/- 3 to 78 +/- 3 mmHg during intrarenal infusion of 1 ng.kg-1.min-1 ANP; increasing the ANP infusion rate did not result in a further reduction in MAP. Systemic arterial plasma ANP concentration did not change from control (15 +/- 5 pg/ml) during 1 or 2 ng.kg-1.min-1 intrarenal ANP infusion but increased slightly during 4 ng.kg-1.min-1 intrarenal ANP infusion, averaging 53 +/- 11 pg/ml. Renal arterial plasma ANP concentrations were calculated to increase to approximately 120 +/- 5, 248 +/- 11, and 484 +/- 22 pg/ml during 1, 2, and 4 ng.kg-1.min-1 intrarenal ANP infusion, respectively. Intravenous ANP infusion did not alter MAP at 1 ng.kg-1.min-1, but MAP was slightly lower than control during 2 and 4 ng.kg-1.min-1 ANP infusion and remained below control during the postinfusion period.(ABSTRACT TRUNCATED AT 250 WORDS)