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J Exp Biol. 2017 Nov 15;220(Pt 22):4234-4241. doi: 10.1242/jeb.164137. Epub 2017 Sep 22.

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

Author information

1
Department of Biology, Saint Louis University, St Louis, MO 63109, USA.
2
University of Kentucky, Department of Physiology and Division of Cardiovascular Medicine, Lexington, KY 40536, USA.
3
Department of Biology, Saint Louis University, St Louis, MO 63109, USA daniel.warren@slu.edu.

Abstract

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.

KEYWORDS:

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

PMID:
28939564
DOI:
10.1242/jeb.164137
[Indexed for MEDLINE]
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