In this study, we examined the effects of exposure of heart fatty acid-binding protein (h-FABP) to chemically generated O2- or OH. with respect to its oleate binding and to its electrophoretic properties. Purified rat h-FABP at 40 microM scavenged as much as 30% O2- and 85% OH.. On the other hand, when 2 nmol (4 microM) FABP were exposed to free radicals, the maximum oleate binding capacity as measured by Scatchard analysis was reduced only by 14% and 27% for O2- and OH., respectively. The electrophoretic pattern of free radical-exposed FABP was not markedly different when examined either by the non-denaturing or by denaturing PAGE, suggesting the absence of any degradation or aggregation of FABP by O2- or OH.. It is hypothesized that O2- or OH. in physiological concentration may not alter the function of FABP markedly in the ischemic-reperfused myocardium.

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PubMedDate not supplied

Preconditioning of heart by repeated stunning: adaptive modification of myocardial lipid membrane.

Recent studies indicate that preconditioning of the heart by repeated stunning protects it from subsequent ischemic injury. Such myocardial preservation is likely to be due to adaptive modification of lipid composition and dynamic structure of cellular membrane. To test this hypothesis, swine heart was subjected to four episodes of 5 min stunning by LAD occlusion, followed by 10 min of reperfusion after each stunning. The heart was then made regionally ischemic for 60 min by LAD occlusion, followed by 6 h reperfusion. A control heart was perfused for 60 min, followed by 60 min ischemia and 6 h reperfusion. Free fatty acids (FFA) accumulated in the control heart during ischemia, as expected, which was further enhanced by reperfusion. The FFA level was also enhanced during ischemia in stunned myocardium. However, this FFA level was almost restored during reperfusion. The levels of unsaturated fatty acids (UFA) such as oleate, linoleate, and arachidonate followed a similar pattern. Membrane fluidity, monitored by fluorescence polarization, was decreased during ischemia and reperfusion in the unstunned heart, with the corresponding increase in microviscosity. The increased microviscosity was significantly reduced by stunning. Since FFA are presumably generated from membrane phospholipids, these results suggest that stunning may cause the incorporation of a greater proportion of PUFA in membrane phospholipids, leading to preservation of membrane phospholipids and maintaining the membrane fluidity, which may be at least partially responsible for the attenuation of ischemic reperfusion injury.

Adaptation, Physiological↗

PubMedDate not supplied

Enhanced membrane protein kinase C activity in myocardial ischemia.

The protein kinase activity in cytosol was similar in control, ischemic, and reperfused hearts; however, a 1.5-fold increase in membrane protein kinase activity was induced by ischemia and reperfusion. The H-7 inhibitable cytosolic protein kinase activity decreased by 40% with 30 min ischemia, while that of membrane fraction increased 1.8-fold. However, the CGS9343B inhibitable protein kinase activity in cytosolic fractions was unaffected by ischemia, while that of membrane increased by about 1.7-fold. These results suggest that myocardial ischemia is associated with enhanced protein kinase C and calmodulin-dependent kinase activities in membrane fraction. Furthermore, the results also suggest a translocation of protein kinase C activity from the cytosol to the membrane. Reperfusion of ischemic myocardium did not result in any further increase of protein kinase C and calmodulin-dependent kinase activities in the membrane. These enhanced protein kinase activities also resulted in an enhanced phosphorylation of endogenous membrane proteins. The creatine kinase released from the heart was increased by both ischemia and reperfusion. Therefore, these results suggest that biochemical cascades of reactions caused by enhanced membrane protein kinase C and calmodulin-dependent kinase activities may contribute to ischemic-reperfusion injury.

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PubMedDate not supplied

Components of variation under sib-mating with linkage.

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Animals↗