Effects of Atrial Natriuretic Peptides and Furosemide in Conscious Dogs

Abstract

Abstract

Effects of ANF(8–33) and Auriculin A on renal variables were investigated in conscious water-diuretic dogs. The two substances were injected intravenously (1.08 μg/kg in 3 min) or ANF(8–33) was infused (0.2 μg/kg × min in 20 min). The effects were compared to those of an equinatriuretic dose of furosemide (1.0 μg/kg × min). Injections caused increases in sodium excretion, diuresis, and osmolar clearance. No significant change in exogenous creatinine clearance (C_CREA) occurred. Infusion of ANF(8–33) decreased blood pressure by 14% (P < 0.01) and increased sodium excretion by a factor of 10 (P < 0.01). The natriuresis was a function of increases in diuresis and urinary sodium concentration, the latter by a factor of 6 (P < 0.01). Diuresis and free-water clearance (C_H2O) increased by 60% (P < 0.01), but urine osmolality did not change significantly. After the infusion a significant decrease in PAH clearance (C_PAH) (P < 0.01) was observed. Filtration fraction (FF) did not change. The furosemide natriuresis appeared later than that of ANF without significant deviations in diuresis, C _H2O, C_CREA, C_PAH, and FF; urine osmolality increased by 35% (P < 0.01). The effects of ANF(8–33) differ from those of furosemide in several ways. First, the onset of natriuresis is faster; second, the natriuresis is associated by marked increases in diuresis and free-water clearance but not in urine osmolality; and third, natriuresis is followed by a reduction in renal blood flow. The rapid natriuresis of ANF can occur without changes in glomerular filtration rate.