Lysosomal activation in mouse skeletal muscle induced by protamine in vitro.
Incubation of mouse skeletal muscle in a physiological Ringer solution containing protamine (60 microgram/ml) at +37 degrees C for 1 h induced ultrastructural changes including proliferation of tubular profiles and vesicles at the I-band level close to the A-I junction, formation of numerous acid phosphatase positive lysosomes in the longitudinal sarcoplasmic reticulum and autophagic vacuolation starting at the level of the A-I junction. Biochemical determination of acid phosphatase in the incubated muscles showed that protamine caused an increase in acid phosphatase activity of about 25% compared to enzyme activities obtained from muscles incubated without protamine at +37 degrees C or with protamine at +4 degrees C. The morphological findings suggest that the vesicles arising adjacent to the A-I junction originate from transverse tubules. Such vesicles, designated as endocytic, may acquire acid phosphatase activity in the longitudinal SR ano be active in an autophagic process resulting in large vacuoles. A causal relationship between endocytosis and lysosomal activation is suggested.
D000135:Acid Phosphatase / Q000032:analysis; D000818:Animals; D004705:Endocytosis; D008247:Lysosomes / Q000187:drug effects* / Q000201:enzymology / Q000648:ultrastructure; D008297:Male; D051379:Mice; D008854:Microscopy, Electron; D009132:Muscles / Q000187:drug effects* / Q000648:ultrastructure; D011479:Protamines / Q000494:pharmacology*; D012519:Sarcoplasmic Reticulum; D014617:Vacuoles
D011479:Protamines; D000135:Acid Phosphatase