Trypsin induces Ca²⁺‐activated Cl⁻ currents in X. laevis oocytes

The protease trypsin induces Ca(2+)-activated Cl- currents when applied in concentrations as low as 0.1 mg/ml to defolliculated, voltage clamped X. laevis oocytes. The response is dose-dependent and specific, as other proteases (chymotrypsin, Lys-C and Arg-C), or trypsin pretreated with soybean trypsin inhibitor, did not induce currents. Intracellular trypsin injection did not induce responses. The current does not appear to result from proteolytic activation of the endogenous receptor for lysophosphatidic acid, the only known Ca(2+)-mobilizing receptor consistently present in oocytes. These results suggest the presence on the oocyte membrane of a specific receptor for trypsin.