Thermal diversities of two Na+/H+ exchanges in guinea pig red cells.
OBJECTIVE
To test the effect of hypothermia on Na+/H+ exchange, activated by shrinkage and cytoplasmic acidosis.


METHODS
Amiloride-sensitive Na+ influx in guinea pig red cells was traced with isotope 22Na and intracellular Na+ concentration was measured by emission flame photometry.


RESULTS
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.


CONCLUSIONS
These two modes of Na+/H+ exchange with different response to elevated temperature may play different roles in the cellular pathogenesis of heatstroke.
Ji
H L
HL
Department of Cellular Biology, University of Georgia, Athens, Georgia 30602, USA. ji@physiology.uab.edu
D000818:Animals; D018929:Cell Culture Techniques; D004912:Erythrocytes / Q000502:physiology; D006168:Guinea Pigs; D018883:Heat Stroke / Q000503:physiopathology*; D006859:Hydrogen / Q000493:pharmacokinetics*; D007474:Ion Exchange; D012964:Sodium / Q000493:pharmacokinetics*; D013696:Temperature
D006859:Hydrogen; D012964:Sodium