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Lysosomal activation in mouse skeletal muscle induced by protamine in vitro
Abstract:
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.
Insights
Protamine induces ultrastructural changes in mouse skeletal muscle, including lysosome formation and autophagic vacuolation. This suggests protamine activates cellular processes related to muscle cell degradation and repair.
Area of Science:
- Cell Biology
- Muscle Physiology
- Biochemistry
Background:
- Skeletal muscle undergoes complex ultrastructural changes in response to stimuli.
- Lysosomes and autophagic processes are crucial for cellular homeostasis and degradation.
- Acid phosphatase is a key enzyme marker for lysosomal activity.
Purpose of the Study:
- To investigate the ultrastructural and biochemical effects of protamine on mouse skeletal muscle.
- To elucidate the role of protamine in cellular degradation pathways within muscle tissue.
Main Methods:
- Incubation of mouse skeletal muscle with protamine (60 microgram/ml) at 37°C for 1 hour.
- Morphological analysis using electron microscopy to observe ultrastructural changes.
- Biochemical assays to determine acid phosphatase activity in muscle homogenates.
Main Results:
- Protamine induced proliferation of tubular profiles and vesicles near the A-I junction.
- Increased formation of acid phosphatase-positive lysosomes in the sarcoplasmic reticulum was observed.
- Autophagic vacuolation initiated at the A-I junction level.
- A 25% increase in acid phosphatase activity was measured in protamine-treated muscles compared to controls.
Conclusions:
- Protamine triggers significant ultrastructural alterations in skeletal muscle.
- Endocytic vesicles, potentially originating from transverse tubules, may be involved in lysosomal activation.
- Protamine exposure suggests a causal link between endocytosis and lysosomal activity, promoting autophagy.