BALLOON DILATATION OF PORCINE PULMONARY-ARTERIES DECREASES ENDOTHELIUM-DEPENDENT RELAXATIONS AND INCREASES VASOCONSTRICTION TO AGGREGATING PLATELETS

Background Balloon dilatation of muscular coronary arteries disrupts e ndothelium and smooth muscle and allows platelet aggregation and adher ence and cell proliferation, which can lead to restenosis. Balloon dil atation of the more distensible pulmonary artery is commonly performed , but the extent of damage to endothelium and its effect on the releas e of endothelium-derived nitric oxide (EDNO) and prostacyclin has not been studied. Methods and Results We dilated distal pulmonary arteries of intact ex vivo porcine lungs (n=20; balloon-dilated [BD] group) us ing similar-sized adjacent vessels as controls with (E+ group) and wit hout (E- group) endothelium. Isolated rings were studied in vitro. Agg regating platelets caused constrictions of quiescent rings from the BD (27.4+/-8% of constriction to 80 mmol/L KCl) and E- groups (24+/-5%), which were inhibited by pyrilamine, a histamine blocker (11+/-4%; P<. 05), and an intact endothelium (8+/-5%; P<.05). Constrictions to hista mine and KCl were similar in the BD and E- groups. In rings with incre ased tone, platelets caused endothelium-dependent relaxations in the E + group (70+/-6% relaxation), which were significantly (P<.05) inhibit ed in the BD group (20+/-7%), by L-nitro-arginine (EDNO blocker, 17+/- 7%) and in the E- group (21+/-9%). Balloon dilatation markedly reduced endothelium-dependent relaxations to 5-hydroxytryptamine, thrombin, a cetylcholine, and the calcium ionophore A23187, but relaxations to sod ium nitroprusside were unaffected. Conclusions Despite the distensibil ity of the pulmonary artery, balloon dilatation significantly damages the pulmonary endothelium, decreases EDNO production, impairs vasodila tion, and favors platelet-induced vasoconstriction. 0