The effects of pH and Pi on tension and Ca2+ sensitivity of ventricular myofilaments from the anoxia-tolerant painted turtle

Cornelia E. Fanter, Kenneth S. Campbell, Daniel E. Warren

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


We aimed to determine how increases in intracellular H+ and inorganic phosphate (Pi) to levels observed during anoxic submergence affect contractility in ventricular muscle of the anoxia-tolerant Western painted turtle, Chrysemys picta bellii. Skinned multicellular preparations were exposed to six treatments with physiologically relevant levels of pH (7.4, 7.0, 6.6) and Pi (3 and 8 mmol l-1). Each preparation was tested in a range of calcium concentrations (PCA 9.0-4.5) to determine the PCA-tension relationship for each treatment. Acidosis significantly decreased contractility by decreasing Ca2+ sensitivity (PCA50) and tension development (P<0.001). Increasing [Pi] also decreased contractility by decreasing tension development at every pH level (P<0.001) but, alone, did not affect Ca2+ sensitivity (P=0.689). Simultaneous increases in [H+] and [Pi] interacted to attenuate the decreased tension development and Ca2+ sensitivity (P<0.001), possibly reflecting a decreased sensitivity to Pi when it is present as the dihydrogen phosphate form, which increases as pH decreases. Compared with that of mammals, the ventricle of turtles exhibits higher Ca2+# sensitivity, which is consistent with previous studies of ectothermic vertebrates.

Original languageEnglish
Pages (from-to)4234-4241
Number of pages8
JournalJournal of Experimental Biology
Issue number22
StatePublished - Nov 15 2017

Bibliographical note

Funding Information:
This work was supported by National Science Foundation CAREER grant 1253939 awarded to D.E.W.

Publisher Copyright:
© 2017. Published by The Company of Biologists Ltd.


  • Acidosis
  • Calcium
  • Contractility
  • Force development
  • Inorganic phosphate
  • Reptile

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Physiology
  • Aquatic Science
  • Animal Science and Zoology
  • Molecular Biology
  • Insect Science


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