Hemodynamic and renal effects of atrial natriuretic factor (99-126) in volume expanded sheep

The renal and hemodynamic effects of atrial natriuretic factor 99-126 (ANF) were examined in hypervolemic sheep and the results compared to responses previously observed in normal isovolemic sheep. Infusion of 500 ml dextran over 60 min increased blood pressure by 6 +/- 2 mmHg, associated with increases in cardiac output and stroke volume. No change was seen in heart rate nor total peripheral resistance. Subsequent infusion of ANF at 100 micrograms/h for 60 min reduced blood pressure by 6 +/- 1 mmHg and decreased stroke volume and cardiac output. There was no change in heart rate. Total peripheral resistance decreased slightly, to a similar degree to that seen after control infusion of 500 ml dextran. Moderate increases in urine volume, sodium and chloride excretion were seen after infusion of dextran and subsequent infusion of ANF markedly enhanced these renal effects. The renal changes produced by ANF in volume expanded sheep were significantly greater than those observed in normal sheep. Although normal sheep are more sensitive to the hemodynamic than to the renal effects of ANF, after dextran pretreatment there was enhancement of the renal responses with little change in the effects on blood pressure.