The effect of acidosis on excitation-contraction coupling in isolated ferret heart muscle.
The contractile response to acidosis is the final product of a number of different changes in the excitation-contraction coupling pathway: (i) Cai increases and subsequently decreases during acidosis; (ii) the action potential becomes longer; (iii) the sensitivity of the contractile proteins to Ca2+ decreases. The increase of Cai and the lengthening of the action potential may help to maintain contractile function, although this advantage may be offset if spontaneous Ca2+ release from the s.r. occurs, secondary to the increase of Cai. The recovery of force shown in figure 1 occurs at a time when the calcium transient is decreasing, and therefore represents an increasing sensitivity of the contractile proteins to Cai, probably due to a recovery of intracellular pH (6), although it is also possible that a disappearance of spontaneous Ca2+ releases from the s.r. may be contributing [2].
Orchard
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Department of Physiology, University of Leeds, UK.
D000138:Acidosis / Q000378:metabolism*; D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004594:Electrophysiology; D005289:Ferrets; D006863:Hydrogen-Ion Concentration; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism*
D002118:Calcium