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Thermal diversities of two Na+/H+ exchanges in guinea pig red cells
1Department of Cellular Biology, University of Georgia, Athens, Georgia 30602, USA. ji@physiology.uab.edu
Objective:
To test the effect of hypothermia on Na+/H+ exchange, activated by shrinkage and cytoplasmic acidosis.
Method:
Amiloride-sensitive Na+ influx in guinea pig red cells was traced with isotope 22Na and intracellular Na+ concentration was measured by emission flame photometry.
Result:
Amiloride-sensitive Na+ influx decreased linearly as a function of temperatures (about 37 degrees C) in shrunken cells, but increased in acidified cells. The up-regulation of acid-induced Na+/H+ exchange by elevated temperature was enhanced by hypo-osmolarity. Less sensitivity of intracellular H+ site at 41 degrees C may be the mechanism for the inhibition of shrinkage-induced Na+/H+ exchange by elevated temperature. Heating-mediated explosive increase in the activity of acid-induced Na+/H+ exchange may be due to enhanced extracellular Na+ sensitivity and lower intracellular pH caused by acidic metabolites. Acid-induced Na+/H+ exchange contributes to cytoplasmic Na+ accumulation.
Conclusion:
These two modes of Na+/H+ exchange with different response to elevated temperature may play different roles in the cellular pathogenesis of heatstroke.
