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Myosin changes in experimental 2,4‐dichlorophenoxyacetate myopathy
Author(s) -
Muhlrad Andras,
Friedman Margalit
Publication year - 1978
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880010606
Subject(s) - myosin , proteolysis , chemistry , myopathy , trypsin , medicine , chymotrypsin , gel electrophoresis , endocrinology , biochemistry , enzyme , biology
Young rats treated with 10 to 14 daily injections of 2,4‐dichlorophenoxyacetate (2,4‐D) developed a myopathy mainly involving fast muscles. Myosin isolated from the gastrocnemius muscles of treated and normal control animals differed in several respects. The Ca 2+ − and Mg 2+ ‐mediated ATPases were higher in myopathic muscle myosin than in normals. Alkylation of thiols by N‐ethylmaleimide (NEM) induced an increase of Ca 2+ ‐activated ATPase that was higher in normal than in myopathic myosin. Trinitrophenylation of reactive amino groups by 2,4,6‐trinitrobenzene sulfonate (TBS) induced an increase in Mg 2+ ‐mediated ATPase in both preparations, but the increase was higher in normals. Although the heavy‐ and light‐chain pattern was identical in normal and myopathic myosin, during storage at 0°C the relative amount of myopathic L 2 light chain decreased. Myosins fragmented either by limited proteolysis with trypsin and chymotrypsin or by specific cleavage at tryptophanyl and cysteinyl peptide bonds showed differences on sodium dodecylsulfate (SDS)‐polyacrylamide‐gel electrophoresis. The results indicate that there is a change in the heavy chains of myosin isolated from the gastrocnemius muscle in 2,4‐D‐induced rat myopathy.