CARDIOVASCULAR EFFECTS OF LONG-TERM ENDOTHELIN INFUSION AND RESPONSES TO ENDOTHELIN DURING ACTH INFUSION IN CONSCIOUS SHEEP

Abstract

Infusion of endothelin-1 (ET-1) (2000 pmol/h) into conscious sheep for 6 days caused a sustained increase in mean arterial pressure (MAP) of 19 +/- 1 mm Hg. This response was mediated by the vasoconstrictor effect of ET-1 and was accompanied by a fall in cardiac output. Plasma renin concentration fell throughout the infusion and atrial natriuretic peptide was increased on day 1 of ET-1 infusion. Hematocrit dramatically increased, probably mainly due to plasma loss resulting from the ET-1-induced increased capillary hydrostatic pressure. To determine whether increased pressor responsiveness to ET-1 played a role in the rise in MAP caused by corticotropin (ACTH), the responses to bolus doses o..