Faculty Collaboration Database

Contractile, biochemical, and histochemical properties of thyrotoxic rat soleus muscle. Am J Physiol 1980 Jan;238(1):C14-20

Date

01/01/1980

Pubmed ID

6444499

DOI

10.1152/ajpcell.1980.238.1.C15

Scopus ID

2-s2.0-0018814373 (requires institutional sign-in at Scopus site)   53 Citations

Abstract

The effects of thyrotoxicosis on the contractile properties of soleus muscle were examined in rats given 3 mg of T4 and 1 mg of T3 per kg of diet for 6--8 wk. Thyrotoxicosis induced significant decreases in isometric twitch contraction time (CT), one-half relaxation time, and peak twitch tension. The Ca2+ uptake activity of the sarcoplasmic reticulum (SR) was increased in the thyrotoxic muscles; this adaptation in the SR provides a possible mechanism for the alterations in isometric contractile properties. Thyrotoxicosis induced a large increase in fibers classified as type 2, on the basis of an alkali-stable histochemical reaction for ATPase, in the soleus. Although this reaction is commonly interpreted as indicating that a muscle is fast, maximum shortening velocity (Vmax) and Mg2+ activated actomyosin ATPase activity were unaffected in the thyrotoxic soleus. Our findings provide evidence that CT and Vmax can vary independently and that the histochemical ATPase reaction may not always reflect the biochemical properties that make myosin fast or slow.

Author List

Fitts RH, Winder WW, Brooke MH, Kaiser KK, Holloszy JO

Author

Robert Fitts PhD Professor in the Biological Sciences department at Marquette University

MESH terms used to index this publication - Major topics in bold

Adenosine Triphosphatases
Animals
Calcium
Female
Histocytochemistry
Hyperthyroidism
In Vitro Techniques
Magnesium
Muscle Contraction
Muscles
Rats
Sarcoplasmic Reticulum