ACETYLCHOLINESTERASE ACTIVITY IN FAST-TWITCH SKELETAL-MUSCLE FROM THYROIDECTOMIZED RATS

Hypothyroidism is associated with muscle weakness and slowed movements . Hormone-deficient muscles do show changes in contractile proteins an d sarcoplasmic calcium pumps, however effects on the components of the neuromuscular-junction are less clear. In this study, we examined cho linesterase activity in adult fast-twitch muscle from hypothyroid and control rats. Male Holtzman rats underwent thyroidectomy and their age -matched euthyroid controls were simultaneously subjected to sham oper ation. Thirty days post-operative, animals were sacrificed for anterio r tibialis muscles harvest. Muscle cholinesterase isoform activity was measured and compared between experimental treatment groups. Butyrylc holinesterase activities and peak I and m acetylcholinesterase (AchE) activities were similar in euthyroid and hypothyroid groups. However, hypothyroid muscles exhibited half the peak II AchE isoform (G4) activ ity, as compared to control muscles. Hypothyroidism specifically affec ts AchE isoform expression in rodent fast-twitch muscle.