Heat production during contraction in skeletal muscle of hypothyroid mice
- Free Univ., Amsterdam (Netherlands)
The effect of hypothyroidism on tension-independent and -dependent heat produced during a twitch and a tetanic contraction of extensor digitorum longus (EDL) and soleus muscle of mice was examined. The amount of heat produced during a twitch and the rate of heat development during a tetanus of EDL and soleus were measured at and above optimal length. The effect of hypothyroidism on force production was <30%. Straight lines were used to fit the relation between heat production and force. Hypothyroidism significantly decreases tension-independent heat during contraction of EDL and soleus muscle. Because the tension-independent heat is considered to be related to the Ca{sup 2+} cycling, these findings suggest that ATP splitting due to the Ca{sup 2+} cycling is reduced in hypothyroid mice. This conclusion was strengthened by the observation that the oxalate-supported {sup 45}Ca{sup 2+}-uptake activity and {sup 45}Ca{sup 2+}-loading capacity of muscle homogenates from hypothyroid mice were reduced, respectively, to 51 and to 65% in soleus and to 63 and 73% in EDL muscle as compared with euthyroid mice. The tension-dependent rate of heat development during a tetanus was also decreased in soleus muscle of hypothyroid mice. This suggests a lower rate of ATP hydrolysis related to cross-bridge cycling in this muscle due to the hypothyroid state.
- OSTI ID:
- 5026515
- Journal Information:
- American Journal of Physiology; (USA), Vol. 253:2; ISSN 0002-9513
- Country of Publication:
- United States
- Language:
- English
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CALCIUM 45
UPTAKE
HYPOTHYROIDISM
RADIOINDUCTION
MUSCLES
PHYSIOLOGY
ATP
CALCIUM COMPOUNDS
CONTRACTION
ENZYMATIC HYDROLYSIS
IODINE 131
MICE
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALCIUM ISOTOPES
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
DECOMPOSITION
DISEASES
ENDOCRINE DISEASES
EVEN-ODD NUCLEI
HYDROLYSIS
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPES
LYSIS
MAMMALS
NUCLEI
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
RADIOISOTOPES
RODENTS
SOLVOLYSIS
VERTEBRATES
551001* - Physiological Systems- Tracer Techniques