EFFECT OF ENALAPRILAT ON SPLANCHNIC VASCULAR CAPACITANCE DURING ACUTEISCHEMIC HEART-FAILURE IN DOGS

This study investigates the effect of angiotensin- converting-enzyme i nhibition by intravenous enalaprilat (100 mu g/kg) on splanchnic vascu lar capacitance during acute left ventricular failure induced by coron ary microembolization in alpha-chloralose/ urethan anesthetized dogs. Changes in hepatic and splenic vascular volumes were determined from o rgan diameters (sonomicrometry) at 15, 30, and 45 min after enalaprila t injection. Changes in vascular capacitance were assessed from organ pressure-diameter curves obtained during transient hepatic outflow occ lusion. Thirty minutes after enalaprilat, hepatic volume was increased by 52 +/- 14 ml (P < 0.01), and portal and hepatic vein pressures wer e decreased from 10.2 +/- 0.9 to 8.7 +/- 0.8 mmHg (P < 0.01) and from 3.9 +/- 1.6 to 3.1 +/- 0.7 mmHg (P < 0.05), respectively. Splenic volu me did not change. Enalaprilat shifted the hepatic pressure-diameter c urve upward, resulting in a larger hepatic volume at any given pressur e. Curve intercept was increased, suggesting an increase in unstressed vascular volume. Curve slope was unchanged. In conclusion, enalaprila t increased hepatic vascular volume during acute left ventricular fail ure in dogs. The pressure-diameter curve shift suggests a reduction in the smooth muscle tone of hepatic capacitance vessels.