title: Hormone-responsive alkaline proteinase in rat skeletal muscle is not a mast cell-derived enzyme.
abstract: Proteinase activity was determined in myofibrils from intact rat skeletal muscle and from skeletal muscle myocytes grown in culture. In vivo administration of the mast cell degranulator compound 48/80 abolished the alkaline proteinase activity in myofibrils obtained from normal or streptozotocin-diabetic rats. Exposure of myocytes to compound 48/80 in cell cultures had no effect on their myofibrillar proteinase activity, nor did it affect the rate of overall protein degradation in these cells. Co-incubation of cultured mast cells (line P815Y) with myocytes followed by sonication of the cell mixture resulted in a marked reduction of the proteinase activity in the pellet fraction, suggesting that the mast cells contain inhibitor(s) of myofibrillar proteinase activity. It is suggested that the myofibril-bound alkaline proteinase activity is not a mast cell-derived enzyme but a genuine component of muscle cells. The in vivo 48/80-induced reduction of muscle myofibrillar proteinase activity appears to be due to release of a soluble inhibitory activity rather than removal of mast cell proteinase from the tissue by degranulation.
mesh_terms: D000818:Animals; D002460:Cell Line; D003594:Cytoplasmic Granules / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology; D010450:Endopeptidases / Q000378:metabolism*; D008297:Male; D008407:Mast Cells / Q000201:enzymology*; D009132:Muscles / Q000201:enzymology*; D009210:Myofibrils / Q000201:enzymology; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
chemical_list: D011480:Protease Inhibitors; D003189:p-Methoxy-N-methylphenethylamine; D010450:Endopeptidases