Endothelin receptor mediated Ca2+ signaling in coronary arteries after experimentally induced ischemia/reperfusion injury in rat

- Stretch-induced tone is increased after ischemia/reperfusion (I/R) injury.
- Upon ligand activation, ETB-Rs have weaker Ca2+-sensitizing effect than ETA-Rs.
- Augmented ETB-R evoked contraction after I/R is dependent on Ca2+ influx.
- Following I/R, ETA-R Ca2+ handling became more dependent on Ca2+ release from SR.

BackgroundAcute myocardial infarction is one of the leading causes of death. It is caused by a blockage of a coronary artery leading to reduced blood flow to the myocardium and hence ischemic damage. In addition, a second wave of damage after the flow has been restored, named reperfusion injury greatly exacerbate the damage. For the latter, no medical treatment exist. In this study the aim was to characterize Ca2+ sensitivity in coronary arteries following experimental ischemia/reperfusion injury.MethodsArteries were isolated from hearts exposed to a well-established rat ischemia/reperfusion model. Wire myograph combined with FURA2-AM measurements was applied to study the Ca2+ dependency of the vasoconstriction.ResultsThe results presented herein show that ETB receptors (R) have much weaker Ca2+-sensitizing effect than ETA-R and that ETB-R appear to be more dependent on Ca2+ influx presumably through voltage-gated Ca2+ channels (VGCC). In addition, we show that there is an increase in the stretch-induced tone after ischemia/reperfusion, and that this increase in tone is independent of the ETB-R upregulation.ConclusionOur data support the theory that ischemia/reperfusion may induce a phenotypical shift, which includes increased evoked ETB induced contraction in the smooth muscle cell, and also a higher basal tone development which both are dependent on Ca2+ influx through VGCCs. This is combined with alterations in the ETA calcium handling, which has a stronger dependence on Ca2+ release from the sarcoplasmic reticulum after I/R injury.