Characterization of an Na+/K+/Cl- co-transport in primary cultures of rat astrocytes.

The furosemide- and bumetanide-sensitive component of the 86Rb+ uptake into primary cultures of rat astrocytes was fully dependent on the simultaneous presence of Na+ and Cl- in the incubation mixture and is therefore most likely an Na+/K+/Cl- co-transporter. As expected for such a co-transporter, its activity is insensitive to 0.1 mM amiloride and to 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid, and of the tested anions, only Br- could partly replace Cl-. The K0.5 values for K+, Na+ and Cl- activation were 2.7, 35 and 40 mM, respectively. The activity of the co-transporter was stimulated 1.5-times in hyperosmolar (500 mosM) medium.