Prostacyclin infusion does not prevent ACTH-induced hypertension in sheep

The present experiments examine the hemodynamic effects of an intravenous infusion of prostacyclin on the development of ACTH-induced hypertension in conscious sheep. Prostacyclin was infused at either 0.01 microgram/kg min-1 for 9 days or 0.25 microgram/kg min-1 for 4 days. At 0.01 microgram/kg min-1 prostacyclin had no effect on blood pressure in normotensive sheep or on the development of ACTH hypertension. Infusion at 0.25 microgram/kg min-1 increased heart rate, cardiac output and plasma renin concentration and decreased stroke volume and peripheral resistance in normotensive sheep. Despite these effects it did not prevent development of ACTH-induced hypertension. It is unlikely on the basis of these results that glucocorticoid-induced inhibition of vasodepressor prostacyclin and resulting increase in pressor responsiveness to circulating agonists is the primary cause of ACTH induced hypertension in sheep.