Homeostasis of Sodium and Potassium Ions in Erythrocytes of the Lamprey Lampetra fluviatilis: Effect of Ion Transport and Metabolic Blockers, and Ionophores

Abstract

After incubation of lamprey Lampetra fluviatilis erythrocytes in the standard medium for 90–120 min, intracellular Na+ and K+ content remained unchanged (28.7 ± 1.1 and 66.3 ± 1.5 mmol/l cells, respectively, n = 33). The erythrocyte ion content also did not change after treatment of the cells with ion transport inhibitors, Ba2+ and amiloride. Addition of 0.1 mM ouabain to the incubation medium led to a decrease of K+ content by 8.4 ± 1.2 and to an increase of Na+ content by 2.4 ± 0.8 mmol/l/2 h. Similar reciprocal changes in the cellular ion composition were observed after treatment of the erythrocytes by oxidative metabolism inhibitors (rotenone and CCCP—carbonyl cyanide m-chlorophenyl-hydrazone). The metabolic blockers produced more significant ion composition changes in comparison with ouabain. An increase of intracellular Na+ content under effect of CCCP was completely inhibited by amiloride. It can be suggested that inhibition of oxidative metabolism is accompanied by a cell acidification and Na+/H+ exchange activation. Erythrocyte acidification by a K+/H+ ionophore led to a rapid cellular Na+ accumulation, which indicates the presence of a Na+/H+ exchanger with high activity. The K+ ionophore valinomycin produced a relatively small K+ loss from the lamprey erythrocytes to indicate a low anion conductance of the cells. The data obtained indicate an important role of oxidative metabolism in the monovalent ion homeostasis in the lamprey red blood cells.