Cardiomyocyte intracellular calcium and cardiac dysfunction after burn trauma.

OBJECTIVE

To examine the effects of pharmacologic agents designed to limit burn-mediated calcium overload on cardiomyocyte [Ca2+] and cardiac contractile function.

DESIGN

Experimental, comparative study.

SETTING

Cellular biology and physiology laboratory.

SUBJECTS

Adult Sprague Dawley rats.

INTERVENTIONS

Rats were given third-degree burn injury over 40% of the total body surface area, were fluid resuscitated, and then were divided randomly to receive one of five treatments: vehicle (normal saline); amiloride (50 mg/kg) to inhibit H+-Na+ exchange and subsequent Na+-Ca2+ exchange; dantrolene (10 mg/kg, 30 mins, 6 and 22 hrs postburn) to inhibit sarcoplasmic reticulum Ca2+ release; diltiazem (10 mg/kg given over first 6 hrs postburn); or amlodipine (0.07 mg/kg, 24 hrs preburn and 30 mins postburn) to block calcium slow channels. Appropriate controls (sham burns given the appropriate pharmacologic agent) were included in each group. Twenty-four hrs postburn, left ventricular function (Langendorff), cardiomyocyte [Ca2+]i and [Na+]i measured by fura-2-AM or sodium-binding benzofurzan isophthalate loading of cardiomyocytes, and myocyte secretion of tumor necrosis factor-alpha (enzyme-linked immunosorbent assay) were assessed in shams and burns from each experimental group. This time point was selected based on our previous work confirming maximal ventricular contractile defects and maximal cytokine secretion 24 hrs postburn.

MEASUREMENTS AND MAIN RESULTS

Burn trauma increased myocyte [Ca2+]i and [Na+]i, promoted tumor necrosis factor-alpha secretion by cardiomyocytes, and impaired left ventricular function. All pharmacologic agents reduced the burn-mediated Ca2+/Na+ accumulation in cardiomyocytes and ablated burn-mediated tumor necrosis factor-alpha secretion by myocytes; in contrast, dantrolene and amiloride provided significantly greater cardioprotection than pharmacologic agents that specifically targeted Ca2+ slow channels (diltiazem and amlodipine).

CONCLUSION

Our data suggest that the calcium antagonists used in this study provide cardioprotection by modulating several aspects of the overall inflammatory cascade rather than solely limiting cardiomyocyte accumulation of calcium.