Effects of synthetic atrial natriuretic factor on renal function and renin release

Studies were performed in anesthetized dogs (n = 5) to determine the effects of synthetic atrial natriuretic factor on renal function and renin release. Intrarenal infusion of synthetic atrial natriuretic factor (ANF) (0.3 μg·kg^-1·min^-1) resulted in a transient increase in renal blood flow (126 ± 8 to 148 ± 11 ml/min). The duration of this transient vasodilation was 3.1 ± 0.4 min. Continued infusion was followed by a slight decrease in renal blood flow (126 ± 8 to 117 ± 8 ml/min) and an increase in glomerular filtration rate (23.1 ± 3.5 to 30.7 ± 1.9 ml/min), with filtration fraction thus being increased (0.19 ± 0.04 to 0.27 ± 0.03). These hemodynamic alterations were associated with increases in fractional sodium excretion (0.6 ± 0.2 to 5.8 ± 0.8%), fractional potassium excretion (30.8 ± 9.4 to 56.3 ± 7.4%), fractional lithium excretion (32.2 ± 7.1 to 60.3 ± 5.7%), and fractional phosphate excretion (8.7 ± 3.5 to 41.6 ± 11.7%). Intrarenal infusion of synthetic ANF markedly suppressed renin secretion rate (295.5 ± 84.6 to 17.2 ± 10.6 ng/min) despite a slight reduction in arterial pressure (123 ± 9 to 118 ± 9 mmHg). Our studies demonstrate that synthetic ANF results in a marked natriuretic response that is in part mediated by an increase in glomerular filtration rate. The increase in fractional lithium and phosphate excretion suggests that this factor may also have an action on proximal tubule reabsorption. Further, these studies demonstrate that synthetic ANF markedly inhibits renin secretion.