Effects of prostaglandin E1 and isosorbide dinitrate on acute hypoxic pulmonary vasoconstriction in conscious sheep.

The pulmonary vascular effects of prostaglandin E1 (PGE1) and isosorbide dinitrate (ISD) on acute hypoxic pulmonary vasoconstriction in conscious sheep were studied. While the animals inhaled room air or hypoxic gas (O2:N2 = 1:9), PGE1 (0.5 microgram/kg/min) and ISD (10 microgram/kg/min) were administered intravenously for 20 min, using an infusion pump. The changes of pulmonary arterial pressure (PPA) or pulmonary vascular resistance (PVR) in room air due to PGE1 were not significant, but in the hypoxic condition, PGE1 decreased PPA by 14.7% (p less than 0.05) and PVR by 14.5% (p less than 0.05). The effect of PGE1 in room air on systemic arterial pressure (PSA) remained nearly constant, whereas slight decreases in systemic vascular resistance (SVR) were noticed. In hypoxic condition, PSA levels were slightly decreased by PGE1, but SVR indicated a slight degree of delayed rise. When ISD in room air was administered, the values of PPA, PVR, PSA and SVR decreased by 9% (p less than 0.05), 10.4% (p less than 0.05), 17.7% (p less than 0.05) and 21.8% (p less than 0.05), respectively. In hypoxic condition, ISD decreased the values of PPA, PVR, PSA and SVR by 14.7% (p less than 0.05), 15.8% (p less than 0.05), 10.2% (p less than 0.05) and 6.7% (p less than 0.05), respectively. In summary in hypoxic condition both PGE1 and ISD cause similar decreases of PPA and PVR. Furthermore, there was a very little decrease in PSA during PGE1 infusion in the hypoxic condition.(ABSTRACT TRUNCATED AT 250 WORDS)