Comparison of 2 endothelin-receptor antagonists on in vitro responses of equine palmar digital arterial and venous rings to endothelin-1.

TL;DRAbstract

The goals of this study were to determine the concentration-response (C-R) relationship of endothelin-1 (ET-1), compare 2 ET-receptor antagonists and determine the antagonist concentrations that block the vasomotor effects of ET-1, and compare the effectiveness of ET-1 and previously studied vasoconstrictors in equine palmar digital arterial and venous rings in vitro. Vessel rings from 8 nonlaminitic horses were placed in Tyrode's solution, 1 side fixed to the floor of an organ bath and the other side fixed to a force-displacement transducer. Two separate studies were conducted: (I) incubation with a single ET-receptor antagonist (PD142893 or PD145065 at a concentration of 10(-7), 10(-6), or 10(-5) M), followed by determination of an ET-1 C-R curve (using concentrations of 10(-10) to 10(-6) M) for medial vessel rings; and (II) comparison of ET-1 with norepinephrine and histamine (10(-10) to 10(-6) M) and comparison of contractile responses of medial and lateral vessel rings. In study I

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