Effects of Calcium Channel Blockade on the Hemodynamic Responses to Endothelin Infusion in Conscious Sheep

The hemodynamic responses to bolus injection of endothelin I (ET) at 5,15, and 50 µg were examined in conscious sheep (n = 5) before and after infusion of nisoldipine at 25 µg/kg/h. Endothelin produced dose-dependent increases in mean arterial pressure (MAP + 87 ± 6 mm Hg at 50 µg) and calculated total peripheral resistance (CTPR + 54 ± 15 mm Hg/L/min at 50 µg) and decreases in heart rate (HR – 34 ± 6 beats/min at 50 µg) and cardiac output (CO – 2.6 ± 0.3 L/min at 50 µg) but no change in stroke volume (SV). Nisoldipine attenuated (P