Contractile shortening response of ventricular cells to extracellular acidosis. Evidence for two-site control of H+-Ca2+ interaction

Circulation Research
G A LangerS Ji


The effect of extracellular acidosis on contraction of single isolated ventricular cells from rabbit was measured in a system in which pHo could be changed in less than 200 msec. The contractile response to acidotic levels was complete within 25 seconds. The response was measured 30 seconds after pHo was decreased to 7.0, 6.5, 6.0, and 5.5 at each of 8 [Ca]o levels (0.125-4.0 mM). Cell shortening versus [Ca]o was plotted to construct a curve for each pHo level, with each point relative to shortening at pH 7.5, [Ca]o = 1 mM (100% value). Calcium current (1 mM [Ca]o) was also measured 30 seconds after pHo was decreased from 7.5 to 6.5 with single-cell patch clamp technique. The contractile response to extracellular acidosis is accurately predicted by assuming two (probably sarcolemmal) sites at which H+ ions affect calcium binding and/or flux: (equation; see text) The first factor represents a set of sites that are proposed to control access, dependent on the degree of their ionization, to sites represented by the second factor. The latter sites are proposed to accept calcium according to mass-action law. The response of calcium channel current to extracellular acidosis was also complete and reversible within 25 seconds. The curr...Continue Reading


Aug 1, 1990·Cardiovascular Drugs and Therapy·L H Opie
May 1, 1993·Archives Internationales De Physiologie, De Biochimie Et De Biophysique·S M MoscaH E Cingolani
Nov 11, 1991·The American Journal of Physiology·T NakanishiK Momma

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Myocardial Contraction
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