DIFFERENTIAL-EFFECTS OF PROLONGED SEPTICEMIA ON ISOLATED PULMONARY-ARTERIES AND VEINS FROM SHEEP

Isolated third-order pulmonary arteries and veins from sheep were exam ined for the effects of septicemia on norepinephrine-induced contracti ons, nitric oxide INO)-mediated dilation, and basal cyclic GMP levels. The groups studied were as follows: control sheep (n = 7); sheep give n live Pseudomonas aeruginosa (Ps, n = 6) for 48 h; and sheep given N- G-mono-methyl-L-arginine during the last 24 h of Ps infusion (Ps-L-NMM A, n = 4). The norepinephrine-induced contractions were significantly greater (p < .05) in arteries from septic (Ps and Ps-L-NMMA) sheep. Ba sal cyclic GMP levels were similar in all of the arteries. The norepin ephrine-induced contractions were significantly depressed (p < .05) in veins from septic (Ps and Ps-L-NMMA) sheep. Basal cyclic GMP levels i n veins from Ps sheep were markedly elevated (p < .01). N-omega-nitro- L-arginine methyl ester (L-NAME) ex vivo decreased cyclic GMP in both arteries and veins. Removal of endothelium enhanced contractions and d ecreased cyclic GMP in arteries and veins only from control sheep. The results show that septicemia differently affects the pulmonary artery and vein. The enhanced vasoconstriction of the artery is due to decre ased endothelium-dependent NO release; the attenuated vasoconstriction of the vein is associated with NO-mediated increased cyclic GMP level s.