Temperature-dependent shift of pHi in fish white muscle: contributions of passive and active processes
Van Dijk, P.L.; Hardewig, I.; Pörtner, H.O.
American Journal of Physiology 272(1 Pt 2): R84-R89
1997
ISSN/ISBN: 0002-9513 PMID: 9038994 Document Number: 483691
This study was designed to determine the mechanisms causing temperature-induced pH shifts in the white muscle of the marine teleost Zoarces viviparus. The white musculature undergoes an intracellular acidification with increasing body temperature at a slope of the pH-temperature relationship equal to -0.016 +- 0.003 U/ degree C. This is in good accordance with the overall relationship between the change in pK and the change in temperature of the intracellular proteins, which was determined to be -0.013 +- 0.001 U/ degree C. Thus the dissociation state of muscle proteins is kept fairly constant in white muscle of Zoarces viviparus. The passive component of the observed pH shift, which is due to the physicochemical response of the intracellular buffers to temperature change, accounts for only 35% of the pH transition. Ventilatory adjustment of intracellular PCO-2 does not contribute to the temperature-induced shift of intracellular pH (pH-i) in Zoarces viviparus. Therefore, the remaining 65% of pH adjustment must be ascribed to ion exchange mechanisms. The nonbicarbonate buffer value amounted to 34.4 +- 2.3 meq cntdot pH-1 cntdot kg cell water-1 at 12 degree C and decreased slightly but not significantly with temperature. On the basis of our data we calculated that a removal of 0.52 mmol base equivalents cntdot kg cell water-1 cntdot degree C-1 was necessary to shift pH-i to its new steady state.