SECRETION OF PLASMINOGEN-ACTIVATOR AND LYSOSOMAL-ENZYMES FROM MOUSE SKELETAL-MUSCLE - EFFECT OF DENERVATION

Levels of hydrolytic enzymes increase in skeletal muscle after denerva tion and their activities in the extracellular matrix appear to be imp ortant for interaction between muscle and nerve. Using enzymatic assay s for beta-glucuronidase, beta-galactosidase, and plasminogen activato r, we show that secretion of these enzymes from mouse skeletal muscle increases after denervation and that drugs interfering with the secret ory pathway or the reuptake of enzymes modulate this release. Thus, br efeldin A inhibited secretion of plasminogen activator activity and ma nnan increased secreted amounts of beta-glucuronidase, but not of beta -galactosidase, in denervated muscle. In innervated muscle, brefeldin A decreased secreted activity of plasminogen activator, but mannan had no effect on secretion of either beta-glucuronidase or beta-galactosi dase. Furthermore, secretion of plasminogen activator was temperature dependent. These observations, together with previous studies, suggest that secretion of hydrolytic enzymes from adult skeletal muscle may b e of physiological significance in nerve/muscle communication. (C) 199 5 Wiley-Liss, Inc.