Sarcoplasmic reticulum Ca2+ transport and long chain acylcarnitines in hyperthyroidism

1988 ◽  
Vol 66 (2) ◽  
pp. 159-165 ◽  
Author(s):  
Shawn C. Black ◽  
John H. McNeill ◽  
Sidney Katz
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Transport ◽  
Wistar Rats ◽  
Free Calcium ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Calcium Dependent ◽  
Endogenous Level ◽  
Male Wistar Rats ◽  
Carnitine Derivatives ◽  
Long Chain

Male Wistar rats were treated with L-3,5,3′-triiodothyronine (T3) (500 μg∙kg∙−1∙day−1) for 3 days. Cardiac sarcoplasmic reticulum (SR) was isolated at several time points during the induction of the hyperthyroid state and calcium transport and the levels of carnitine derivatives were determined. Calcium transport was augmented at all free calcium concentrations assayed (0.1–5.3 μM) 24 h following a single dose of T3; at 48 and 72 h, calcium transport was further augmented. Calcium-dependent phosphoprotein levels were increased in the SR of the 48- and 72-h T3-treated groups. Total SR carnitine was reduced after 24, 48, and 72 h of treatment. Long chain acylcarnitine (LCAC) levels were decreased in T3-treated SR at 48 and 72 h. This study shows that calcium transport is increased in T3-treated rat heart SR and that this increase may be related to a reduction in the endogenous level of LCAC in the SR membrane.

Alteration of Acylphosphate Formation of Cardiac Sarcoplasmic Reticulum ATPase by Calmodulin-Dependent Phosphorylation

1984 ◽  
Vol 39 (3-4) ◽  
pp. 289-292 ◽  
Author(s):  
Christian Pifl ◽  
Brigitte Plank ◽  
Gertrude Hellmann ◽  
Wolfgang Wyskovsky ◽  
Josef Suko
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Transport ◽  
State Level ◽  
Hill Coefficient ◽  
Free Calcium ◽  
Sr Protein ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Transport Atpase ◽  
Calcium Dependent ◽  
Calcium Calmodulin Dependent

The calcium-dependent acylphosphate formed by the calcium transport ATPase of cardiac sarcoplasmic reticulum and the calcium-, calm odulin-dependent phosphoester(s) of sarcoplasmic reticulum fractions formed by a calcium-, calmodulin-dependent membrane-bound protein kinase can be distinguished by removal of calcium and/or magnesium by EDTA or hydroxylamine treatment of the acid denaturated membranes. Both procedures decompose the acylphosphate with little effect on the phosphoester(s). Calmodulin-dependent phosphorylation (2.44 nmol/mg SR protein) reduces the apparent K(Ca) of the acylphosphate steady state level of the calcium transport ATPase from 0.56 to 0.34 μM free calcium, without affecting the maximum phosphoenzyme level (0.93 versus 0.89 nmol/mg protein), and has little, if any, effect on the Hill-coefficient (1.32 versus 1.54)

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.

Pressure Effects on the Interactions of the Sarcoplasmic Reticulum Calcium Transport Enzyme with Calcium and para-Nitrophenyl Phosphate

1987 ◽  
Vol 42 (5) ◽  
pp. 641-652 ◽  
Author(s):  
Wilhelm Hasselbach ◽  
Lore Stephan
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Transport ◽  
Activation Volume ◽  
Reaction Scheme ◽  
Pressure Effects ◽  
Calcium Dependent ◽  
Nitrophenyl Phosphate ◽  
Hydrolysis Of ◽  
Sarcoplasmic Reticulum Calcium ◽  
Effect Of Hydrostatic Pressure

The effect of hydrostatic pressure on calcium dependent p-nitrophenyl phosphate hydrolysis of the sarcoplasmic reticulum calcium transport enzyme has been investigated at different degree of enzyme saturation by calcium and Mg-p-nitrophenyl phosphate to distinguish between activation and binding volumes. The enzyme saturated by both ligands displays a significant dependence of the activation volume on pressure, rising from 20 ml/mol at atmospheric pressure (0.1 MPa) to 80 ml/mol at 100 MPa. At subsaturating concentration of Mg-p-nitrophenyl phosphate an activation volume of 35 ml/mol prevails between 0.1 and 40 MPa. At subsaturating concentration of calcium the activation volume approximates 80 ml/mol in the same pressure range. The binding volume for both substrates is likewise pressure dependent falling from 20 ml/mol to 0 ml/mol for Mg-p-nitrophenyl phosphate and rising from 67 ml/mol to 155 ml/mol for calcium. The pressure dependence of activation and binding volumes is analysed on account of a simplified reaction scheme yielding activation volumes and rate constants for individual reaction steps.

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