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EFFECTS OF THYROXINE TREATMENT ON CONTRACTIONS OF SOLEUS MUSCLES OF ANAESTHETIZED CATS
Author(s) -
Merican Zainuddin,
Morat Paden
Publication year - 1984
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1984.tb00857.x
Subject(s) - medicine , soleus muscle , endocrinology , chemistry , cats , propranolol , tonic (physiology) , tetanic stimulation , contraction (grammar) , skeletal muscle , long term potentiation , receptor
SUMMARY 1. The effects of chronic thyroxine treatment on cat soleus muscle contractions were studied. 2. Maximum twitch tension, contraction time, half relaxation time and tensiontime integral of maximal twitches of the soleus muscles of thyroxine treated cats were significantly decreased. Consequently, there was a decrease in tension and degree of fusion of incomplete tetanic contractions of the soleus muscle. The maximum tetanic tension was not statistically significantly changed, suggesting that the effects may be due to a decrease in the duration of the active state of the muscle. 3. Isoprenaline given intravenously during incomplete tetanic contractions of the soleus muscle caused a statistically significant depression of tension in the control group but not in the thyroxine treated group. This further suggests reduction in the duration of the active state of soleus muscles of thyroxine treated cats. 4. Propranolol injected chronically with thyroxine reversed or prevented the depression of tension caused by thyroxine treatment, suggesting the involvement of β‐adrenoceptors in these effects. 5. The decrease in tension and degree of fusion during incomplete tetanic contractions of the thyroxine treated soleus could be responsible, at least partly, for the muscle weakness and tremor of thyrotoxicosis. Cyclic AMP may possibly be the mediator of these effects.