CHARACTERIZATION OF MONO-VALENT ION-TRANSPORT SYSTEMS IN AN INSECT CELL-LINE (MANDUCA-SEXTA EMBRYONIC-CELL LINE CHE)

The monovalent ion transport systems of an immortalized insect cell line (CHE) were investigated. These cells are unusual in that unlike most vertebrate cells, their normal extracellular environment consists of high K and low Na concentrations. CHE cells maintained high intracellular [K+] through both a furosemide-inhibitable and a vanadate-inhibitable transport system. Intracellular exchangeable [Na+] was slightly lower than the extracellular [Na+] and was maintained at this level through a vanadate-sensitive transport system. Na+ uptake was also inhibited by furosemide; however, the stoichiometry of furosemide-sensitive Na+ uptake when compared with furosemide-sensitive K+ uptake indicated that these cations are not cotransported. 4,4''-Diisothiocyano-2,2''-disulfonic acid stilbene (DIDS) inhibited Na+, K+ and Cl- uptake. Vanadate and furosemide decreased cytoplasmic pH, while cytoplasmic pH increased in the presence of DIDS. A model is presented explaining how Na+, K+, Cl-, H+ and HCO3- fluxes are regulated in these cells.