title: Release of unassembled rat cardiac myosin light chain 1 following the calcium paradox.
abstract: To determine the intracellular source and release kinetics of myosin light chain 1 immediately following irreversible myocytic injury, we perfused rat hearts in a Langendorff apparatus under control conditions (20 minutes), or during global cellular injury produced by oxygenated, calcium-free perfusion (5 minutes), followed by reperfusion with buffer containing 2.5 mM calcium (15 minutes). Light chain 1 concentration (double antibody radioimmunoassay) and creatine kinase activity were measured in both the coronary effluent and the 140,000 g supernatant extract of perfused ventricular tissue (after homogenization and ultracentrifugation). Calcium reperfusion caused the rapid release of both light chain 1 and creatine kinase activity (peak light chain 1 = 1.09 +/- 0.19 micrograms/g; peak creatine kinase = 74.9 +/- 10.7 IU/ g at 1 minute, mean +/- SD, n = 3); 28.5 +/- 13.5% of total light chain 1 and 86.5 +/- 0.6% of total creatine kinase activity were depleted from the tissue extract during the 15-minute reperfusion. No light chain 1 or creatine kinase was detected in the effluents of control-perfused hearts. Dodecyl sulfate polyacrylamide gel electrophoresis and immunodetection with specific antibody to myosin heavy chain and light chain 1 showed that the effluent light chain 1 was of similar molecular weight (mol wt = 27,000) to the subunit bound to myofibrils. In addition, light chain 1 was released in the absence of myosin heavy chain. Thus, a small soluble pool of unassembled myosin light chain 1 subunits exists in the cytoplasm of cardiac myocytes that is released from irreversibly injured cells. This pool demonstrates initial washout kinetics similar to creatine kinase.
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D002118:Calcium / Q000008:administration & dosage / Q000494:pharmacology*; D003327:Coronary Disease / Q000378:metabolism*; D003402:Creatine Kinase / Q000378:metabolism; D006168:Guinea Pigs; D007106:Immune Sera / Q000276:immunology; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009218:Myosins / Q000276:immunology / Q000378:metabolism*; D010477:Perfusion; D011863:Radioimmunoassay; D051381:Rats
chemical_list: D007106:Immune Sera; D003402:Creatine Kinase; D009218:Myosins; D002118:Calcium