Prominent depressor response to endothelin in spontaneously hypertensive rats

Abstract

Administration of endothelin (0.03–3.0 μg/kg i.v.) caused transient depressor responses followed by sustained pressor responses in anaesthetized spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). The initial depressor response occured at lower doses (0.1 versus 0.3 μg/kg i.v.) in SHR versus WKY. The secondary pressor response was attenuated in SHR compared to WKY in both the threshold dose (3.0 versus 0.1 μg/kg i.v.) and maximum effect at high doses (52 versus 91% at 3.0 μg/kg i.v.). In conscious SHR and WKY, endothelin elicited comparable initial depressor responses with increases in heart rate; the secondary pressor responses were attenuated compared to those in anesthetized rats. Therefore endothelin elicits a prominent depressor response, which maybe associated with afterload reduction, in SHR.