Uptakes of iodide and chloride by primary cultures of mouse astrocytes and neurons.

Primary cultures of both mouse astrocytes and neurons accumulate more 125I- than 36Cl- from the medium. The average cell/medium ratio of 125I- of astrocytes (1.01) is greater than that of neurons (0.74), whereas the ratio of 36Cl- of neurons (0.47) is greater than that of astrocytes (0.25). The equilibrium potentials of both 125I- and 36Cl- calculated from the cell/medium ratios in astrocytes and neurons are significantly lower than their corresponding resting transmembrane potentials which suggest that both iodide and chloride are actively transported into both cell types. With respect to different transport inhibitors, thiocyanate is more effective in inhibiting 125I- uptake whereas furosemide is more effective in inhibiting 36Cl- uptake. Radioiodide uptake by mouse astrocytes was directly proportional to the [Na+]o but was not significantly affected by changes of [Cl-]o or [HCO3-]o, except that it is low in bicarbonate-free medium. Radiochloride uptake by astrocytes was inversely related to [Cl-]o and [HCO3-]o and was not affected [Na+]o, except that it was low in sodium-free medium. Radioiodide uptake by neurons was directly related to [Na+]o between 60 and 140 mM and inversely related to [HCO3-]o between 10 and 40 mM, but it was not affected by [Cl-]o. Radiochloride uptake by neurons was directly related to [Cl-]o and to [Na+]o between 60 and 140 mM and was not affected by [HCO3-]o. However, in sodium-free medium both 125I- and 36Cl- uptakes into neurons were higher than those in [Na+]o between 5 and 60 mM. These results indicate that uptake of 125I- and 36Cl- into astrocytes and neurons are different in their ion dependence and that they are under separate regulation.