Early changes in the ultrastructure of denervated rat skeletal muscle

• Published in: Experimental neurology Vol. 56; no. 1; pp. 115 - 131
• Main Authors: Cullen, Michael J., Pluskal, Malcolm G.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.1977
• Subjects: Animals; Cathepsins - metabolism; Cell Membrane - ultrastructure; Endoplasmic Reticulum - ultrastructure; Fingers; Golgi Apparatus - physiology; Lysosomes - ultrastructure; Muscle Denervation; Muscles - enzymology; Muscles - ultrastructure; Peptide Hydrolases - metabolism; Rats; Receptors, Drug; Ribosomes - ultrastructure; EDL; RER; SR
• ISSN: 0014-4886; 1090-2430
• DOI: 10.1016/0014-4886(77)90143-1

The activities of peptide hydrolase and cathepsin B1, thought to be lysosomal, increase shortly after denervation in the rat soleus and extensor digitorum longus (EDL) muscles. In order to look for evidence of a concomitant formation of lysosomes the ultrastructure was examined at 3 days after denervation, when the activities reach a maximum in the soleus, and at 6 days after denervation, when they reach a peak in the EDL. Morphometry was carried out to quantify some of the changes in the fiber constituents. Both types of muscle showed a heterogeneous range of secondary lysosomes including autophagic vacuoles, multivesicular bodies, myelin figures, and lipofuscin granules. These constituted up to 1% of the volume of the denervated fibers. Also present were small dense bodies which, because of their morphological characterization and their location, were thought to be primary lysosomes. These were often in close association with Golgi complexes which became more numerous after denervation. There was also an increase in ribosomes and rough endoplasmic reticulum (RER). Earlier work suggested that this protein-synthetic machinery is involved in the production of new acetylcholine receptors in the plasma membrane, but the present authors make an alternative suggestion that the new RER and Golgi apparatus are involved in the manufacture and sequestering of the enzymes entering into the lysosomes.