Glass electrode measurement of net Na+ and K+ fluxes in erythrocytes of the spontaneously hypertensive rat.

The exchange of Na+ and K+ in rat red cells at 40% hematocrit incubated in a physiological salt solution containing 1 MM ouabain was monitored with ion-specific glass electrodes. Because this system measures a change in the activity of an ion as a logarithmic function of its preexisting level, delta[K+]o is more accurately measured than delta[Na+]o; within this limitation, the downhill ion movements were close to 1:1 over the temperature span from 37 to 3 degrees C. These transmembrane movements are reasonably well expressed in terms of first-order kinetics and an Arrhenius plot constructed for K+ as the accurate indicator of the exchange yields an activation energy of 12 kcal/mol. A well-defined reversal of the usual direct relation of temperature to exchange rate was observed between 6 and 3 degrees C. The net ion movements were distinctly faster at low temperature in cells from rats with spontaneous hypertension (SHR-Okamoto) than in cells from matched controls (Woodlyn and WKY).