Protein kinase C inhibition improves ventricular function after thermal trauma.

OBJECTIVE To examine the effect of protein kinase C (PKC) inhibition on cardiac performance and intracellular Ca2+ homeostasis. DESIGN Previous studies have shown that trauma impairs cardiac mechanical function, and recent studies suggest that PKC activation and subsequent perturbations in Ca2+ sequestration/release contribute to this cardiac dysfunction. In this study, anesthetized guinea pigs were given third-degree scald burns over 43 +/- 1% of the total body surface area and resuscitated with lactated Ringer's solution (LR) 4 mL/kg per percent of burn, Parkland formula. Animals with sham burns served as controls (n = 18). Burns were randomly divided into two groups: LR alone (N = 18) or LR + PKC inhibitor, calphostin C (0.1 mg/kg, intravenous bolus), given 30 minutes and 3, 6, and 21 hours after burn (n = 18). MATERIALS AND METHODS Cardiac function was assessed by Langendorff preparation 24 hours after burn in 8 to 12 animals per group. Intracellular calcium concentration ([Ca2+]i) was measured in cardiac myocytes (collagenase digestion) from additional animals in each experimental group (n = 5-9 per group) after Fura-2 AM loading of myocytes; fluorescence ratios were measured with a Hitachi spectrofluorometer. RESULTS Cardiac dysfunction occurred 24 hours after burn in LR burns as indicated by lower left ventricular pressure and a reduced rate of left ventricular pressure rise and fall, +/-dP/dt (61 +/- 3 mm Hg, 1,109 +/- 44 mm Hg/s, and 880 +/- 40 mm Hg/s, respectively) compared with values measured in sham-burned animals (86 +/- 2 mm Hg, 1365 +/- 43 mm Hg/s, and 1183 +/- 30 mm Hg/s, respectively; p < 0.05). Ventricular function curves confirmed significant postburn contractile depression despite aggressive fluid resuscitation. Cardiac injury in burned animals was indicated by an increase in perfusate creatine kinase and lactate dehydrogenase, and Ca2+ dyshomeostasis was confirmed by increased myocyte [Ca2+]i (sham 151 +/- 6 vs. burn 307 +/- 20 nmol/L, p < 0.05). PKC inhibition improved all indices of cardiac performance, producing left ventricular pressure (82 +/- 3 mm Hg), +/-dP/dt (1,441 +/- 48 and 1,294 +/- 32 mm Hg/s), and left ventricular function curves that were comparable with those of sham-burned animals. In addition, [Ca2+]i in calphostin-treated burned animals (154 +/- 11 nmol/L) was identical to values in sham-burned animals. CONCLUSION Our data suggest that PKC may serve as a final common pathway in signal transduction events mediating postburn cardiac dysfunction.