[The role of chloride channels and chlorine ions in regulating the in-vitro chorionic gonadotropin-stimulated maturation of oocytes in the clawed toad].

The blocker of chloride channels SITS (4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonic acid) (1 and 10 microM) reliable inhibited maturation of Xenopus laevis oocytes stimulated in vitro by human chorionic gonadotropin (5-40 MU/ml) and decreased the progesterone content of the incubation medium. The effect of SITS was dose-dependent and decreased with the increase of the hormone concentration. When the chloride ions in the medium were substituted for equimolar concentrations of sodium, potassium and calcium glutamates or of sodium or potassium chlorides for, respectively, glutamine and aspartate, the percentage of definitive oocytes (1.2-1.4 mm), maturing under the influence of human chorionic gonadotropin and the progesterone contents of the incubation medium increased, the certain part of smaller oocytes (0.9-1 mm).