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

Calcif Tissue Int. 1983;35(2):195-201. doi: 10.1007/BF02405031.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Transport / drug effects
  • Calcitriol / pharmacology*
  • Calcium / metabolism*
  • Calcium-Transporting ATPases / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Female
  • Male
  • Phosphoproteins / biosynthesis
  • Phosphorylation
  • Rabbits
  • Sarcoplasmic Reticulum / drug effects
  • Sarcoplasmic Reticulum / metabolism*
  • Uremia / enzymology
  • Uremia / metabolism*

Substances

  • Phosphoproteins
  • Calcium-Transporting ATPases
  • Calcitriol
  • Calcium