METABOLITE CHANGES ASSOCIATED WITH HEAT-SHOCKED AVIAN FIBROBLAST MITOCHONDRIA

A previous report from our laboratory (Collier et al 1993) showed that the elongated tubules of mitochondria in the cytoplasm of cultured ch icken embryo fibroblasts collapsed to irregularly shaped structures su rrounding the nuclear membrane after a 1 h heat shock treatment. The n ormal mitochondrial morphology reappeared upon removal of the thermal stress. We have now determined that several changes occurred in mitoch ondrial-related metabolites under these same heat shock and recovery c onditions. Among these were significant decreases in the levels of fum arate and malate and increases in the amounts of aspartate and glutama te. In contrast, other intermediates of the tri-carboxylic acid cycle were unaltered as were levels of ATP and phosphocreatine. The changes observed might result from heat shock-induced changes in enzyme activi ties of the mitochondria, from alterations in the membrane-embedded sp ecialized carrier proteins that transport metabolites between cytosol and mitochondria or from a disorganization of the electron-transport s ystem normally coupled to oxidative metabolism. The rapid recovery, ho wever, suggested that these changes were transient and readily reversi ble.