Differential Effects of Endothelin-1 on Normal and Postischemic Reperfused Myocardium

Abstract
Summary: Using an isolated rat heart preparation and 31P magnetic resonance spectroscopy, we studied the effects of endothelin-1 (ET-1) and U-46619, a thromboxane-A2 analogue, on coronary flow (CF), left ventricular developed pressure (LVP), and high-energy phosphate metabolism under control conditions (normal myocardium) and during postischemic reperfusion (reperfused myocardium). The selected doses of ET-1 and U-46619 reduced CF in the normal myocardium to a similar extent (47.8 ± 1.5% and 48.7 ± 4.6%, respectively). In contrast to ET-1, U-46619 induced a depression of LVP (20.2 ± 6.9% versus 6.8 ± 4.7%; ppp<0.05). This was accompanied by a large decrease in LVP and in levels of high-energy phosphate compounds. Therefore, the effects of ET-1 but not of U-46619 are enhanced in reperfused hearts. This may contribute to the delayed recovery of the postischemic reperfused myocardium.

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