Horton J W, Kaufman T M, White D J, Mahony L
Department of Surgery, University of Texas Southwestern Medical Center, Dallas 75235.
J Surg Res. 1993 Jul;55(1):87-96. doi: 10.1006/jsre.1993.1113.
Cardiac dysfunction occurs after a major burn injury regardless of age; whether burn trauma causes greater myocardial contractile depression in the older subject due to reduced cardiac reserves that normally occur with adult aging is not known. The cellular basis for burn-induced cardiac dysfunction is not known, but several studies have suggested that alterations occur in the rate of Ca2+ delivery to the contractile proteins as well as in the rate of Ca2+ removal from the sarcoplasm by the sarcoplasmic reticulum (SR). To determine if age-related differences in the cardiac contractile response to burn injury are associated with differences in SR Ca2+ transport, an isolated heart preparation was used to examine mechanical function, and myocardial homogenate preparations were used to assess SR Ca2+ transport. Guinea pigs from both age groups (adult, 6-8 months, and senescent, 34-36 months of age) were divided into two subgroups--control and 45% cutaneous scald burn. Cardiac dysfunction associated with adult aging alone was indicated by lower systolic pressure and lower rates of left ventricular (LV) pressure rise and fall, as well as decreased responses to isoproterenol, exogenous Ca2+, increased coronary flow rate, and electrical pacing. Myocardial depression in senescent control hearts was accompanied by a decreased maximal Ca2+ uptake in myocardial homogenates, suggesting that altered SR calcium transport may contribute to the diminished contractile function associated with aging. Burn injury impaired cardiac function in all animals regardless of age as evidenced by a leftward shift of LV function curves and altered responses to receptor- and nonreceptor-mediated inotropic interventions. However, the percentage change in cardiac function after burn injury was similar in both age groups compared to those of their respective controls. Significant alterations in SR Ca2+ transport were observed in myocardial homogenates isolated from both adult and senescent hearts after burn injury. Our data confirm that burn injury induced cardiac contractile dysfunction as well as alterations in SR Ca2+ transport function regardless of age, and we conclude that altered SR Ca2+ transport function contributes, in part, to the diminished cardiac function after burn injury.
无论年龄大小，严重烧伤后都会出现心脏功能障碍；由于成年衰老通常会导致心脏储备减少，烧伤创伤是否会在老年受试者中引起更大的心肌收缩抑制尚不清楚。烧伤诱导的心脏功能障碍的细胞基础尚不清楚，但多项研究表明，钙离子向收缩蛋白的传递速率以及肌浆网（SR）从肌浆中清除钙离子的速率均发生了改变。为了确定烧伤损伤后心脏收缩反应的年龄相关差异是否与SR钙离子转运差异有关，采用离体心脏标本检测机械功能，并使用心肌匀浆标本评估SR钙离子转运。两个年龄组（成年，6 - 8个月；衰老，34 - 36个月）的豚鼠被分为两个亚组——对照组和45%皮肤烫伤组。仅与成年衰老相关的心脏功能障碍表现为收缩压降低、左心室（LV）压力上升和下降速率降低，以及对异丙肾上腺素、外源性钙离子、冠状动脉血流速率增加和电起搏的反应降低。衰老对照组心脏的心肌抑制伴随着心肌匀浆中最大钙离子摄取量的降低，这表明SR钙离子转运改变可能导致与衰老相关的收缩功能减弱。烧伤损伤使所有动物的心脏功能受损，无论年龄大小，这可通过LV功能曲线向左移位以及对受体介导和非受体介导的变力干预反应改变来证明。然而，与各自对照组相比，两个年龄组烧伤损伤后心脏功能的百分比变化相似。烧伤损伤后，在成年和衰老心脏分离的心肌匀浆中均观察到SR钙离子转运的显著改变。我们的数据证实，无论年龄大小，烧伤损伤都会诱导心脏收缩功能障碍以及SR钙离子转运功能改变，并且我们得出结论，SR钙离子转运功能改变部分导致了烧伤损伤后心脏功能减弱。
