Significance of renal vasodilation after administration of atrial natriuretic factor in the conscious dog.

The contribution of alterations in renal hemodynamics to the diuretic and natriuretic actions of atrial natriuretic factor (ANF) was studied in chronically instrumented conscious dogs. Injection of ANF-(99-119), 10 micrograms/kg, had no effect on mean arterial pressure, heart rate, renal blood flow, or calculated renal vascular resistance; However, it increased urine flow rate (86 +/- 20%) and sodium (118 +/- 24%) and potassium (35 +/- 22%) excretion (p less than 0.05). In contrast, ANF-(99-122), 10 micrograms/kg, significantly increased renal blood flow (26 +/- 4.5%), reduced renal vascular resistance (24 +/- 2.9%) and arterial pressure (5.5 +/- 1.9%), and markedly increased urine flow rate (198 +/- 34%) and sodium (206 +/- 32%) and potassium (75 +/- 27%) excretion (p less than 0.05), being almost twice as effective in the first 10 minutes as was ANF-(99-119) infusion. During a brief infusion, ANF-(99-122) (10 micrograms/kg/min for 4 minutes) increased renal blood flow (24 +/- 2.7%), heart rate (18 +/- 5.7%), urine flow rate (199 +/- 25%), and sodium (290 +/- 81%) and potassium (104 +/- 17%) excretion. Injection of radioactive microspheres (15 or 9 micron) to measure intrarenal distribution of blood flow during the steady state increase in renal blood flow indicated that ANF-(99-122) infusion preferentially increased outer cortical blood flow. Blood flow in the four zones of the kidney cortex (Zone 1, outer, and Zone 4, inner) increased 96 +/- 25% (Zone 1), 199 +/- 87% (Zone 2), 139 +/- 47% (Zone 3), p less than 0.05, and 25 +/- 28% (Zone 4, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)