Effects of acidosis on phosphorylation of phospholamban and troponin I in rat cardiac muscle

C. Mundiña-Weilenmann, L. Vittone, H. E. Cingolani, C. H. Orchard

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34 Scopus citations


Acidosis inhibits Ca2+ transport by the sarcoplasmic reticulum of cardiac muscle and decreases the Ca2+ sensitivity of the contractile proteins, although the mechanisms underlying these changes are unclear. We have investigated the hypothesis that changes in the phosphorylation of the regulatory proteins phospholamban and troponin I might play a role in the acidosis-induced changes in the function of the sarcoplasmic reticulum and the myofilaments, respectively. Langendorff-perfused rat hearts were labeled with 32P and then perfused with either control (pH 7.4) or acid (pH 6.8) physiological salt solution, in both the absence and presence of isoproterenol. The incorporation of 32P into phospholamban and troponin I was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of sarcoplasmic reticulum and myofibrillar proteins, followed by autoradiography and liquid scintillation counting. The data show that acidosis has no effect on the phosphorylation of phospholamban in the absence of isoproterenol but that, in the presence of isoproterenol, acidosis increased the phosphorylation of phospholamban. However, acidosis increased the phosphorylation of troponin I, in both the absence and the presence of isoproterenol. Acidosis did not alter the adenosine 3',5'-cyclic monophosphate content of the hearts but did inhibit type 1 phosphatase. These data show that acidosis can alter the phosphorylation of these two proteins and suggest that these changes underlie, in part, the changes observed in cardiac muscle during acidosis.

Original languageEnglish (US)
Pages (from-to)C107-C114
JournalAmerican Journal of Physiology - Cell Physiology
Issue number1 39-1
StatePublished - Jan 1 1996


  • pH
  • sarcoplasmic reticulum

ASJC Scopus subject areas

  • Physiology
  • Cell Biology


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