Cardiac responses to burn injury in young and adult guinea pigs

The present study examined functional and biochemical differences in young compared to adult hearts, and determined if developmental differences alter ed the ability of the young heart to respond to burn injury. Compared to th e adult heart, hearts from young sham burns had diminished responsiveness t o isoproterenol, extracellular calcium, and increases in either ventricular filling or coronary flow rate. In contrast, there were no age-related diff erences in maximal calcium uptake (360 +/- 11 vs. 367 +/- 14 nmol/mg) or ca lcium uptake velocity (59 +/- 2 vs. 60 +/- 4 nmol/mg/min) in sarcoplasmic r eticulum (SR) vesicles isolated from adult and compared to young control he arts. Burn injury (43% TBSA for adults, 35% TBSA for young) impaired myocar dial function in all hearts, regardless of age. Age-related differences in adult and young hearts persisted after burn trauma with significantly lower left Ventricular developed pressure (49 +/- 2 vs. 63 +/- 3 mmHg, P < 0.01) , +dP/dt max (860 +/- 89 vs. 1151 +/- 62 mmHg/sec, P < 0.01), and -dP/dt ma x (790 +/- 39 vs. 901 +/- 50 mmHg/sec, P < 0.02) in young vs, adult burn he arts. Burn injury reduced cardiac SR maximal calcium uptake in adults (sham , 360 +/- 11; burn, 298 +/- 12 nmol/mg, P < 0.05), but not in young hearts (sham, 367 +/- 14; burn, 380 +/- 12 nmol/mg); however, burn trauma increase d the SR calcium velocity/capacity ratio in both young and adult burn group s. Our data confirm age-related differences in ventricular performance in y oung and adult guinea pigs; these differences persisted after burn trauma. The burn-mediated changes in SR Ca2+ transport suggest that disturbances in intracellular calcium handling may contribute, in part, to post-burn cardi ac contractile deficits regardless of age.