SUMMARYThe effect of angiotensin-converting enzyme inhibition on regional blood flow was studied in a total of 21 normotensive Wistar rats fed on either low or high salt diet. A new potent angiotensin-converting enzyme inhibitor (CEI), SQ 14,225 was administered intravenously in a dose of 2mg/Kg to the conscious animals, and changes in fractional distribution of cardiac output were determined with a microsphere method.Prior to administration of CEI, there was no significant difference in mean arterial pressure (MAP) or regional blood flow between saltdepleted and salt-loaded rats. With CEI, MAP did not change significantly in either group. Fractional distribution of cardiac output increased to the kidneys (p<0.002), and decreased to the stomach, spleen, and skeletal muscle (p<0.02, p<0.002, and p<0.01, respectively) in the salt-depleted group, while a pattern of blood flow distribution was not changed in the salt-loaded group.These results suggest that angiotensin II plays an important role in regulating regional blood flow in salt-depleted conscious animals, but not in salt-loaded ones.