Effects of renal perfusion pressure on the natriuresis induced by atrial natriuretic factor

Synthetic atrial natriuretic factor (ANF 101-126) was infused at 1, 5, 25, and 125 pmol X kg-1 X min-1 into the renal artery of anesthetized, one-kidney dogs. During administration of 25 and 125 pmol X kg-1 X min-1 of ANF 101-126, fractional sodium excretion (FENa) rose from 1.4 +/- 0.3 to 6.6 +/- 1.1 and 5.6 +/- 1.3% when renal perfusion pressure (RPP) was at its basal level (112 +/- 5 mmHg). When base-line RPP was lowered to 101 +/- 5 mmHg by tightening a suprarenal aortic constriction, the same doses raised FENa to only 5.6 +/- 1.6 and 5.1 +/- 1.6%. A larger reduction of beginning RPP to 82 +/- 4 mmHg suppressed the natriuretic responses to 25 and 125 pmol X kg-1 X min-1 of ANF 101-126 to only 1.4 +/- 0.8 and 0.8 +/- 0.3%, respectively. During the peak natriuretic dose of 25 pmol X kg-1 X min-1, renal vascular resistance (RVR) fell from 0.88 +/- 0.10 to 0.68 +/- 0.07, from 0.78 +/- 0.10 to 0.68 +/- 0.12, and from 0.60 +/- 0.06 to 0.61 +/- 0.06 mmHg X ml-1 X min-1 at RPP = RPP = 112, 101, and 82 mmHg, respectively. ANF 101-126 did not affect glomerular filtration rate (GFR) at any level of RPP tested. In conclusion, the natriuretic responses to ANF 101-126 occurred without changes in GFR and were modulated by the prevailing levels of renal perfusion pressure and renal vascular resistance.