The effect of angiotensin-converting enzyme inhibition on regional blood flow in salt-depleted and salt-loaded normotensive conscious rats.

The 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 2 mg/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 salt-depleted and salt-loaded rats. With CEI, MAP did not change significantly in either group. Fractional distribution of cardiac output increased to the kidneys (p less than 0.002), and decreased to the stomach, spleen, and skeletal muscle (p less than 0.02, p less than 0.002, and p less than 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.