TEMPERATURE-DEPENDENT SHIFT OF PH(I) IN FISH WHITE MUSCLE - CONTRIBUTIONS OF PASSIVE AND ACTIVE PROCESSES

This study was designed to determine the mechanisms causing temperatur e-induced pH shifts in the white muscle of the marine teleost Zoarces viviparus. The white musculature undergoes an intracellular acidificat ion with increasing body temperature at a slope of the pH-temperature relationship equal to -0.016 +/- 0.003 U/degrees C. This is in good ac cordance with the overall relationship between the change in pK and th e change in temperature of the intracellular proteins, which was deter mined to be -0.013 +/- 0.001 U/degrees 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 du e to the physicochemical response of the intracellular buffers to temp erature change, accounts for only 35% of the pH transition. Ventilator y adjustment of intracellular PCO2 does not contribute to the temperat ure-induced shift of intracellular pH (pH(i)) in Zoarces viviparus. Th erefore, the remaining 65% of pH adjustment must be ascribed to ion ex change mechanisms. The nonbicarbonate buffer value amounted to 34.4 +/ - 2.3 meq . pH(-1). kg cell water(-1) at 12 degrees C and decreased sl ightly but not significantly with temperature. On the basis of our dat a we calculated that a removal of 0.52 mmol base equivalents . kg cell water(-1).degrees C-1 was necessary to shift pH(i) to its new steady state.