Rubidium fluxes in Xenopus laevis (Amphibia) erythrocytes induced by swelling and relationship with taurine pathway

Abstract

Rubidium (86Rb+) fluxes were used to probe for K+ uptake in Xenopus erythrocytes in vitro following exposure to various ambient osmolalities. Rb+ uptake is composed of two major components, one which is ouabain-sensitive and linearly related to changes in medium osmolarity, and a smaller (1/10 of total) that was ouabain-insensitive. The latter component that was activated when medium osmolarity was diluted 40% to 166 mOsm/l increased 2.5 times. The ouabain-insensitive K+ uptake was reduced to one-third on replacement of Cl– by other anions and was not influenced by DIDS, an anion transport inhibitor. Cl– uptake that was probed from SO4 2– uptake was tripled on medium dilution and was almost completely inhibited by DIDS (4, 4 diisothiocyanatostilbene-2, 2-disulfonic acid). The β-adrenergic stimulating agonist, isoproterenol, had no effect on these processes. Parallel measurements of Rb+ and taurine uptake in relation to medium osmolarity show different kinetics. Parallel measurements of 86Rb+ and taurine fluxes were made on erythrocytes from Bufo viridis. Based on the dissimilarity of responses on inhibitors and the different kinetics, it is concluded that the two solutes that are engaged in cellular volume regulation are transported separately.