Endothelin receptor mediated Ca signaling in coronary arteries after experimentally induced ischemia/reperfusion injury in rat.

BACKGROUND

Acute 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 Ca sensitivity in coronary arteries following experimental ischemia/reperfusion injury.

METHODS

Arteries 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 Ca dependency of the vasoconstriction.

RESULTS

The results presented herein show that ET receptors (R) have much weaker Ca-sensitizing effect than ET-R and that ET-R appear to be more dependent on Ca influx presumably through voltage-gated Ca 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 ET-R upregulation.

CONCLUSION

Our data support the theory that ischemia/reperfusion may induce a phenotypical shift, which includes increased evoked ET induced contraction in the smooth muscle cell, and also a higher basal tone development which both are dependent on Ca influx through VGCCs. This is combined with alterations in the ET calcium handling, which has a stronger dependence on Ca release from the sarcoplasmic reticulum after I/R injury.