NHE1 inhibition with cariporide before coronary occlusion improved acetylcholine-induced microvascular relaxation compared to vehicle (~55% vs ~35%, P<0.05) but did not alter contractile function.
Does cariporide improve myocardial and coronary microvascular stunning in a rat model of ischemia and reperfusion?
NHE1 inhibition with cariporide before coronary occlusion lessens ischemia-induced microvascular dysfunction but does not improve myocardial contractile stunning in a rat model.
Absolute Event Rate: 55% vs 35%
p-value: p=<0.05
Myocardial ischemia and reperfusion cause myocyte and vascular dysfunction, frequently termed "stunning." We hypothesized that inhibiting the Na(+)/H(+) exchanger subtype 1 isoform (NHE(1)) during ischemia and reperfusion limits myocardial and coronary microvascular stunning. Anesthetized rats completed 2 x 10-min coronary artery occlusions separated by 5-min of reperfusion, followed by 15 or 60 min of reperfusion. Vehicle (saline) or the NHE(1) inhibitor cariporide (HOE-642) was administered 15 min before ischemia and was continued throughout each protocol. After reperfusion, hearts were excised, and the reactivity of resistance arteries (internal diameter, approximately 120 microm) was assessed. The first derivative of left ventricular (LV) pressure, LV developed pressure, and LV systolic wall thickening were depressed (P < 0.05) similarly in vehicle- and cariporide-treated rats during ischemia and after 15 or 60 min of reperfusion compared with sham-operated animals that were not exposed to ischemia (i.e., controls). In vessels obtained after 15 min of reperfusion, the maximal response to acetylcholine-induced relaxation (10(-8)-10(-4) M) was blunted (P < 0.05) in vessels from vehicle- (approximately 35%) and cariporide-treated rats (approximately 55%) compared with controls (approximately 85%). However, the percent relaxation to acetylcholine was greater (P < 0.05) in cariporide-treated rats compared with vehicle-treated rats. Maximal contractile responses to endothelin-1 (10(-11)-10(-7) M) were increased (P < 0.05) similarly in vehicle- and cariporide-treated rats compared with controls. Relaxation to sodium nitroprusside (10(-4) M) was not different among groups. Results were similar in vessels obtained from animals after 60 min of reperfusion. These findings suggest that NHE(1) inhibition before coronary occlusion lessens ischemia-induced microvascular dysfunction for 15-60 min after reperfusion but does not alter myocardial contractile function in the area at risk.
Symons et al. (Mon,) conducted a other in Myocardial ischemia and reperfusion (stunning). Cariporide (HOE-642) vs. Vehicle (saline) was evaluated on Maximal response to acetylcholine-induced relaxation in resistance arteries after 15 min of reperfusion (p=<0.05). NHE1 inhibition with cariporide before coronary occlusion improved acetylcholine-induced microvascular relaxation compared to vehicle (~55% vs ~35%, P<0.05) but did not alter contractile function.
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