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Protective effects of diltiazem during myocardial ischemia in isolated cat hearts
Insights
Diltiazem, a calcium channel blocker, protects cat hearts from ischemia-reperfusion injury. This drug preserves cardiac function and mitochondrial activity, reducing calcium overload during these critical events.
Area of Science:
- Cardiovascular Physiology
- Mitochondrial Biology
- Pharmacology
Background:
- Myocardial ischemia and reperfusion (I/R) injury significantly impair cardiac mechanical function and mitochondrial respiration.
- Calcium overload during I/R contributes to cellular damage and dysfunction.
- Diltiazem is a calcium channel blocker with potential cardioprotective properties.
Purpose of the Study:
- To investigate the cardioprotective effects of diltiazem in an isolated, blood-perfused cat heart model subjected to global ischemia and reperfusion.
- To correlate functional recovery with mitochondrial respiratory activity and cellular calcium content.
Main Methods:
- Isolated, blood-perfused cat hearts were subjected to 60 or 90 minutes of global ischemia, followed by 60 or 120 minutes of reperfusion.
- Left ventricular developed pressure (LVDP) and compliance were measured.
- Mitochondrial respiratory activity and Ca++ content were assessed in isolated mitochondria from ischemic-reperfused myocardium.
Main Results:
- Diltiazem treatment significantly attenuated the decline in LVDP and preserved cardiac compliance compared to untreated hearts.
- Diltiazem prevented the depression of mitochondrial oxygen consumption and respiratory control observed in nontreated hearts.
- Diltiazem inhibited the rise in tissue and mitochondrial Ca++ content during ischemia and reperfusion.
- ATP levels recovered better in diltiazem-treated hearts after I/R.
Conclusions:
- Diltiazem exerts direct cardioprotective effects against myocardial ischemia-reperfusion injury in this model.
- Protection is likely mediated by the inhibition of transmembrane calcium influx, preserving mitochondrial function and mechanical integrity.
Abstract:
The protective effects of diltiazem, a calcium channel blocker, were studied in isolated, blood-perfused cat hearts subjected to 60 or 90 min of global ischemia, followed by reperfusion of 60 or 120 min, respectively. Ischemia-induced alterations of left ventricular (LV) developed pressure (DP) and compliance, measured with an intraventricular fluid-filled latex balloon, were correlated with respiratory activity in vitro of mitochondria isolated from ischemic-reperfused LV myocardium. Nontreated isolated hearts sustained severe declines of LVDP as a result of 60 (-50 +/- 8%) and 90 min (-83 +/- 7%) of ischemia, whereas diltiazem-treated hearts demonstrated only minor losses of LVDP (-17 +/- 8 and -26 +/- 2%). Diltiazem prevented losses of compliance caused by 60 or 90 min of ischemia, which were severe in nontreated hearts after the latter period of ischemia. The progressive deterioration of mechanical function observed in nontreated hearts was paralleled by depressed mitochondrial oxygen consumption and respiratory control. The respiratory activity of mitochondria isolated from cat heart mitochondria. Diltiazem also prevented significant elevations of tissue and mitochondria Ca++ content, reflecting inhibition of Ca++ influx during ischemia and reperfusion. Also, recovery of ATP levels was greater after 60 min each of ischemia and reperfusion in diltiazem-treated hearts. Thus, diltiazem exerts direct, cardioprotective effects during myocardial ischemia, presumably by inhibiting transmembrane Ca++ fluxes.