A critical temperature transition of K+-Na+ exchange in human lymphocytes

Publisher Website
Google Scholar
Abstract
Human lymphocytes were equilibrated for 48 hours at 5‐6 mM K+ex over a range of temperatures between 0 and 37°C, and at 5°C over a range of external K+ levels between 0 and 32 mM. Cell K+ and Na+ contents are normal between 37 and 10′. Below 10′ there is a critical thermal transition in ion contents centering around 3°C. This and the steep sigmoidal isotherms of K+ and Na+ at 5°C confirm the cooperative nature of ion exchange. At 0′, cell K+ is maintained at a concentration that is seven to eight times that of the external medium. Isotopic K+ influx shows smaller, rapidly‐exchanging, and larger, slowly‐exchanging fractions. The latter, which correspond to the saturable, sigmoidal components of cell K+, are slowed by decreasing temperature. Although there is a critical temperature transition of K+‐Na+ exchange, there is no corresponding transition for isotopic K+ exchange, which has an activation energy of 11.6 kcal/mole. The combined ion content and flux data are readily understood by reference to two major concepts of the association‐induction hypothesis: that of rapid solute exclusion from cell water existing in a state of polarized multilayers, and that of solute accumulation limited by adsorption onto and desorption from fixed anionic sites that interact with one another in a critical, cooperative fashion.

This publication has 18 references indexed in Scilit: