Effects of botulinum toxin induced muscle paralysis on endocytosis and lysosomal enzyme activities in mouse skeletal muscle

Tågerud, S.; Libelius, R.; Thesleff, S.

Pflugers Archiv European Journal of Physiology 407(3): 275-278

1986


ISSN/ISBN: 0031-6768
PMID: 3763372
DOI: 10.1007/bf00585302
Accession: 005292810

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Abstract
The effects of botulinum toxin (type A) induced muscle paralysis on endocytosis and lysosomal enzyme activities in skeletal muscle were compared with the effects of surgical denervation. Muscle atrophy, measured as decrease in total muscle protein content, was as large or larger after botulinum toxin treatment as after denervation. Endocytic activity, measured as the in vitro uptake of horseradish peroxidase, and the specific activities of the lysosomal enzymes N-acetyl-.beta.-D-glucosaminidase and cathepsin D were all increased six days after denervation. Only the specific activity of cathepsin D was increased six days after botulinum toxin poisoning. The uptake of horseradish peroxidase and the specific activity of N-acetyl-.beta.-D-glucosamidase were also increased eleven days after poisoning. Transverse sections of eleven days botulinum poisoned muscles from animals injected with horseradish peroxidase showed fibers with dense peroxidase staining similar to those seen in denervated muscle although they seemed to occur less frequently. The results show that increases in endocytic activity and lysosomal enzyme activites may occur in skeletal muscle without the presence of degenerating axons. The differences in effects of surgical denervation and botulinum toxin induced paralysis are discussed in terms of what is known about the mechanism of action of botulinum toxin and the possible functional roles of the two lysosomal enzymes studied.

Effects of botulinum toxin induced muscle paralysis on endocytosis and lysosomal enzyme activities in mouse skeletal muscle