Abstract
Experiments were performed in isolated guinea pig hearts, perfused at constant volume. Left ventricular pressure, left ventricular dp/dt max, coronary vascular pressure and coronary venous pO 2 were measured continuously. Indomethacin (1.4 × 10 −6 M) increased coronary vascular resistance by 15% over control ( p < 0.01) without altering the myocardial contractile force. When PGE 2 (1.4 × 10 −8 M) was subsequently added, it abolished the indomethacin action and lowered the coronary vascular resistance below the pre-indomethacin control value. This increase in coronary vascular resistance caused by indomethacin was also seen when the animals were presented with reserpine and/or the adrenoceptor blocking agents phenoxybenzamine and propranolol, but was prevented completely by previous addition of PGE 2 (1.4 × 10 −7 M). The results provide evidence for possible involvement of endogenous prostaglandin-like substances in the maintenance of coronary vascular resistance in the isolated guinea pig heart.
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