Cardiovascular responses to alpha-melanocyte stimulating hormone during the perinatal period in sheep

Abstract

To determine the effects of alpha-melanocyte stimulating hormone (αMSH) on the circulation of undisturbed fetal sheep and young lambs and to explore possible mechanisms of actions, we examined the responses of ascending aortic blood flow, heart rate, stroke volume, and arterial blood pressure to a single intravenous injection of αMSH, ACTH, cortisol and to αMSH after beta-adrenergic blockade. We also measured cardiac output and organ blood flows before and after αMSH injection by the radionuclide labeled microsphere technique. αMSH increased ascending aortic blood flow from 249 ± 23 to 327 ± 30 ml- min-1-kg-1 (P < 0.001), heart rate from 111 ± 10 to 126 ± 11 min-1, (P < 0.001) and stroke volume from 2.32 ± 0.21 to 2.75 ± 0.20 ml-kg-1, (P < 0.001) in 10 young lambs 15-30-day-old. αMSH decreased mean systemic arterial blood pressure from 42.6 ± 1.7 to 39.3 ±1.6 mmHg (P < 0.001) in fetal sheep and min-1, (P < 0.001) and stroke volume from 2.32 ± 0.21 to 2.75 ± 0.20 ml-kg-1, (P < 0.001) in