The combined 5-HT2 receptor and calcium channel inhibitor LU49938 restores endothelium dependent responses in the regenerated endothelium of the porcine coronary artery

Abstract

Objective: The aim was to evaluate the effect of the combined 5-hydroxytryptamine-2 (5-HT2) receptor antagonist and calcium channel inhibitor LU49938 ((2S)-5-[N-methyl-N-(n-hexyl)] amino-2-isopropyl-2(3.4.5-trimethoxyphenyl)-valeronitrilhydrochloride) on the endothelium dependent responsiveness of porcine coronary arteries with native and regenerated endothelium. Methods: Male Yorkshire pigs were assigned randomly to one of four groups: (1) controls; (2) pigs receiving LU49938 daily (5 mg·kg-1) for four weeks; (3) pigs undergoing balloon de-endothelialisation of the left anterior descending coronary artery; and (4) pigs undergoing balloon de-endothelialisation and receiving LU49938 daily. At four weeks, quantitative coronary angiography, organ chamber experiments, and morphometric studies of the tissues were performed. Results: Treatment with LU49938 did not affect the endothelium dependent responses in native porcine coronary arteries. Intracoronary injection of serotonin caused significantly greater coronary vasoconstriction in group 3 compared with group 4. The cross sectional area of the intima and media of previously de-endothelialised left anterior descending coronary artery increased significantly in group 3, but not in group 4. In arteries with regenerated endothelium, augmented endothelium dependent contractions were noted not only in response to serotonin, but also in response to platelets, noradrenaline, and endothelin-1. The endothelium dependent relaxations to platelets, serotonin, and UK14304 were impaired in the regenerated endothelium, but not those to adenosine diphosphate and SIN-1. However, following four weeks of treatment with LU49938, the pertussis toxin sensitive endothelium dependent responses were restored. The augmented endothelium dependent contraction to endothelin-1 was not altered by the treatment. Conclusions: Chronic treatment with LU49938 restores endothelium dependent, pertussis toxin sensitive, G protein mediated responses in the regenerated endothelium of the porcine coronary artery, and inhibits the intimal thickening following arterial injury.