Selective Endothelial Dysfunction in Porcine Coronary Artery Produced by Incubation in Cell Culture Mediumin vitro

The purpose of this study was to characterize the effect of in vitro incubation on contraction and endothelium-dependent relaxation of vascular smooth muscle. Incubation of porcine coronary artery rings in cell culture medium for 20-22 hrs selectively enhanced maximal 5-HT contraction without affecting KCI (50 mM) or U46619 (30 nM)-induced contraction. Incubation in cell culture medium selectively impaired endothelium-dependent relaxation to 5-HT, while not affecting endothelium-dependent relaxation to bradykinin, indicating a lack of endothelial damage or denudation. Inhibition of nitric oxide (NO) synthase with L-NAME (100 μM) also selectively inhibited 5-HT-mediated relaxation, suggesting that in vitro incubation produced an impairment in receptor-mediated NO release. Contraction to L-NAME (100 μM) was less in incubated porcine coronary artery rings compared to fresh tissue, suggesting that basal NO release was impaired, as well. Incubated rings were not impaired but supersensitive in their ability to relax to the NO donor, sodium nitroprusside, consistent with an impairment in NO release resulting in supersensitivity to direct vasore-laxation by NO. Impairment was also observed for acetylcholine-mediated, NO-dependent relaxation in rat aorta incubated in an identical manner. Thus, the endothelial dysfunction was not particular to 5-HT or to the porcine coronary artery but was a more general phenomenon. The similarities between the endothelial impairment induced by in vitro incubation and that observed in a variety of clinical conditions suggest this to be a potential in vitro model of endothelial dysfunction not requiring mechanical disruption of endothelial cells.