Ketoconazole, an inhibitor of calcium transport in skeletal muscle sarcoplasmic reticulum

1982 ◽  
Vol 38 (4) ◽  
pp. 445-448 ◽  
Author(s):  
A. M. Cheah
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Transport

The Modulation of the Calcium Transport by Skeletal Muscle Sarcoplasmic Reticulum in the Hibernating European Hamster

1991 ◽  
Vol 46 (11-12) ◽  
pp. 1109-1126 ◽  
Author(s):  
◽  
Luisa De Martino ◽  
Barbara Soltau ◽  
Wilhelm Hasselbach
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Transport ◽  
Calcium Uptake ◽  
Calcium Release ◽  
Ion Homeostasis ◽  
Free Calcium ◽  
Type I ◽  
Calcium Dependent ◽  
Calcium Affinity

Calcium transport of skeletal muscle sarcoplasmic reticulum was comparatively studied in hibernating and summer active European hamsters (Cricetus cricetus L.). Crude homogenates from psoas, soleus and mixed skeletal muscles were used. Protein yield was strongly reduced in the muscle homogenates of hibernating hamsters. The calcium concentration in the muscle of hibernating hamsters was increased to a much higher content than in the serum. In the same animals the maximal rate of calcium uptake and the calcium storing capacity of sarcoplasmic reticulum were augmented by 43% and respectively 17%. Kinetic experiments with various concentrations of free calcium revealed in the hibernating animals higher uptake rates and a lower apparent calcium affinity than in the summer active hamsters. Some shift of calcium uptake rate and calcium affinity similar to that of a fast-twitch muscle was also observed in winter active animals kept at 22 C under natural photoperiod. By contrast, the activity of the calcium dependent ATPase was not increased, suggesting a tighter coupling during hibernation between calcium dependent ATP-hydrolysis and calcium transport. No seasonal difference was observed in the calcium release by KCl-caffeine from calcium loaded vesicles of sarcoplasmic reticulum.Proportion and size of fibre types were studied with cold cross sections from psoas and soleus muscles. An average atrophy of about 25% was found during hibernation in both muscles. Cytochemistry revealed, however, a different reduction of cross area between type-I- and type-11-fibres, which reaches values up to 46% in the type-I I-fast-fibres of the slow soleus muscle. Electron microscopy did not show any definite change in the distribution and amount of sarcoplasmic reticulum.The results suggest that during hibernation a modulation in the properties of calcium transport ATPase of sarcoplasmic reticulum occurs to better support the calcium transport function at low temperatures, which in turn warrants the restoration of ion homeostasis in the course of the arousal.

On the Problem of Season and Cold Dependence of Calcium Transport by Skeletal Muscle Sarcoplasmic Reticulum

1990 ◽  
Vol 45 (6) ◽  
pp. 671-675 ◽  
Author(s):  
Bruno Agostini ◽  
Luisa De Martino ◽  
Wilhelm Hasselbach
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Cold Acclimation ◽  
Uptake Rate ◽  
Calcium Transport ◽  
Calcium Uptake ◽  
Kinetic Studies ◽  
Cold Season ◽  
Free Calcium ◽  
Calcium Affinity

Abstract Calcium transport of skeletal muscle sarcoplasmic reticulum from golden hamsters was studied in January and in June on animals kept at 22 °C under natural photoperiod and in January after cold-acclimation at ±2 °C in the dark for 55 days. Crude homogenates from psoas and soleus muscles and from mixed skeletal muscles were used. No differences were observed in the calcium storing capacity of sarcoplasmic reticulum among the three groups of animals. Kinetic studies on the dependence of the calcium uptake rate on the concentration of free calcium revealed a significant increase of the uptake rates and a decrease of the calcium affinity in the control animals sacrificed in winter as compared to those killed in June. Cold-acclimation in winter leads to a further small reduction of the calcium affinity. This shift of calcium uptake rate and affinity in the sense of that of a fast-twitch muscle may be related to the functional demands of the cold season and cold-acclimation respectively.

scholarly journals The Effect of Quinidine on Calcium Accumulation by Isolated Sarcoplasmic Reticulum of Skeletal and Cardiac Muscle

1968 ◽  
Vol 52 (6) ◽  
pp. 955-968 ◽  
Author(s):  
Franklin Fuchs ◽  
Edward W. Gertz ◽  
F. Norman Briggs
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Calcium Transport ◽  
Coupling Mechanism ◽  
Muscle Preparation ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Tension Development ◽  
Calcium Accumulation ◽  
Pharmacologically Active

Quinidine potentiates twitch tension and (at higher concentrations) causes contracture of skeletal muscle whereas the same drug reduces tension development of cardiac muscle. To gain insight into the possible differences in the excitation-contraction coupling mechanism of the two types of muscle the effect of quinidine on calcium accumulation by isolated sarcoplasmic reticulum from skeletal and cardiac muscle was investigated. In a medium containing ATP, Mg++, oxalate, and 45Ca, pharmacologically active concentrations of the drug inhibited calcium accumulation by both skeletal and cardiac sarcoplasmic reticulum. The inhibition of the rates of calcium, uptake by the skeletal muscle preparation ranged from 11% with 10-4M quinidine to 90% with 10-3 M quinidine. With the cardiac muscle preparation the inhibition ranged from 16% with 3 x 10-6 M quinidine to 100% with 10-3 M quinidine. With both preparations the inhibition of calcium transport was accompanied by an inhibition of the Ca++-activated ATPase activity of the sarcoplasmic reticulum. The effect of quinidine on the skeletal sarcoplasmic reticulum supports the hypothesis that this compound produces twitch potentiation and contracture by interfering with intracellular calcium, sequestration. Its effect on cardiac sarcoplasmic reticulum. has been interpreted in terms of the hypothesis that cardiac contractility is a function of the amount of calcium released from the sarcoplasmic reticulum which is in turn dependent upon the absolute calcium content of the reticulum. Hence, following inhibition of calcium transport there would be less calcium available for coupling.

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