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Reversal of decreased phosphorylation of sarcoplasmic reticulum calcium transport ATPase by 1,25-dihydroxycholecalciferol in experimental uremia

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Boland,  Ricardo
Max Planck Institute for Medical Research, Max Planck Society;

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Matthews,  Clifford
Max Planck Institute for Medical Research, Max Planck Society;

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de Boland,  Ana R.
Max Planck Institute for Medical Research, Max Planck Society;

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Ritz,  Eberhard
Max Planck Institute for Medical Research, Max Planck Society;

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Hasselbach,  Wilhelm
Emeritus Group Biophysics, Max Planck Institute for Medical Research, Max Planck Society;

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Citation

Boland, R., Matthews, C., de Boland, A. R., Ritz, E., & Hasselbach, W. (1983). Reversal of decreased phosphorylation of sarcoplasmic reticulum calcium transport ATPase by 1,25-dihydroxycholecalciferol in experimental uremia. Calcified Tissue International, 35(1), 195-201. doi:10.1007/BF02405031.


Cite as: http://hdl.handle.net/21.11116/0000-0003-6334-3
Abstract
When compared to that from sham-operated controls, sarcoplasmic reticulum isolated from skeletal muscle of uremic rabbits had a lower rate of calcium uptake and storing capacity. In vivo administration of 1,25-dihydroxycholecalciferol [1,25(OH)2D3] restored the values in uremic animals toward normal. To obtain information about the mechanisms responsible for these differences, phosphorylation of the calcium transport ATPase was studied. The steady-state levels of phosphoprotein in uremic membranes were lower and returned to normal when the secosteroid was administered. Electrophoresis of the membranes phosphorylated with 32P-inosine triphosphate (32P-ITP) showed that the differences were related to a 100,000 dalton protein. The rate of phosphoprotein formation, determined with 32P-ITP and at 0 degrees C, was considerably lower in uremic than in control animals. Pretreatment with 1,25(OH)2D3 prevented this change. The hypothesis is advanced that the vitamin D metabolite affects the steady-state concentration and rate constant of formation of active sites in the Ca-ATPase. These results may partly explain the altered Ca transport function of the sarcoplasmic reticulum in experimental uremia.