Changes of regional blood flow induced by atrial natriuretic factor (ANF) in conscious rats

The effect of synthetic atrial natriuretic factor (ANF 101-126) has been studied on regional blood flow distribution. Microspheres (15 +/- 3 microns), labelled with either 113Sn or 57Co, were injected through an intraventricular cannula into conscious rats while a reference blood sample was withdrawn. Two minutes after the first microspheres injection either ANF or NaCl were injected. Five minutes later, the second microspheres injection was administered, and after two minutes the animals were sacrificed, and several tissues removed and counted. Percent of flow distribution, cardiac output and tissue blood flow were calculated by standard formulas. ANF produced a significant increase in absolute blood flow in lungs, heart, spleen, kidneys and testes. Total renal blood flow and total splanchnic blood flow were also increased in ANF-injected animals. No significant changes were observed in cardiac output. It is suggested that the natriuretic and hypotensive responses to ANF in vivo may be, at least partially, explained by its hemodynamic effects.