Inhibition by cAMP of Calcium-Activated Chloride Currents in Cultured Sertoli Cells from Immature Testis

Abstract.

We have characterized a Ca²⁺-dependent Cl⁻ current (Cl_Ca) in cultured Sertoli cells from immature rat testis by using the whole cell recording patch-clamp technique. Cells dialyzed with pipette solutions containing 3 mm adenoside-triphosphate (ATP) and 1 μm free Ca²⁺, exhibited outward currents which were inhibited by 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) and anthracene-9-carboxylic acid (9-AC) but insensitive to tetraethylammonium (TEA). Dialysis of cells with pipette solutions containing less than 1 nm free Ca²⁺ strongly reduced the currents indicating that they were Ca²⁺ dependent. With cells dialyzed with Cs⁺ glutamate-rich pipette solutions containing 0.2 mm EGTA, 10 μm 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_Ca 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 cAMP in primary culture of Sertoli cells and the release of a low Cl⁻ and bicarbonate-rich primary fluid by these cells.