Inhibition by cAMP of calcium-activated chloride currents in cultured Sertoli cells from immature testis

We have characterized a Ca2+-dependent Cl- current (Cl-Ca) in cultured Sert oli cells from immature rat testis by using the whole cell recording patch- clamp technique. Cells dialyzed with pipette solutions containing 3 mM aden oside-triphosphate (ATP) and 1 mu M free Ca2+. exhibited outward currents w hich were inhibited by 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid ( DIDS) and anthracene-9-carboxylic acid (9-AC) but insensitive to tetraethyl ammonium (TEA). Dialysis of cells with pipette solutions containing less th an 1 nM free Ca2+ strongly reduced the currents indicating that they were C a2+ dependent. With cells dialyzed with Cs' glutamate-rich pipette solution s containing 0.2 mM EGTA, 10 mu M ionomycin induced outward currents having properties of Ca2+-activated Cl- currents. With ATP-free pipette solution, the magnitude of currents was not modified suggesting the direct control by Ca2+. By contrast, addition of 0.1 mM cAMP in the pipette solution or the superfusion of cells by a permeant analogue of cAMP strongly reduced the currents. These results may suggest that Cl-C a is inhibited by cAMP-dependent protein kinase. Finally, our results do not agree with the model of primary fluid secretion by exocrine cells, but are in agreement with a hyperpolarizing effect of c AMP in primary culture of Sertoli cells and the release of a low Cl- and bi carbonate-rich primary fluid by these cells.