[The role of chlorine ions in progesterone production and oocyte maturation induced by a pituitary suspension in the follicles of the common frog].

Chloride channel blockers SITS (4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonic acid) and DIDS (4,4'-diisothiocyanostilbene-2,2'-disulphonic acid) significantly suppressed progesterone production (0.01-10 microM) in Rana temporaria follicle-enclosed oocytes and oocyte maturation (0.1-10 microM) stimulated by the homologous pituitary suspension (0.00125-0.005 pit/ml). Inhibition was dose-dependent. SITS (1 and 10 microM) did not affect the production of progesterone stimulated by dibutyrylcyclic AMP (2 and 3 mM). The substitution of chloride salts for equimolar concentrations of corresponding gluconates or of sodium chloride for sodium methanesulfonate also significantly increased the production of progesterone stimulated by the pituitary suspension (0.00125-0.0025 pit/ml) and its production in the intact follicle-enclosed oocytes in four out of six females. The reduction of extracellular chloride concentration significantly potentiated the "spontaneous" maturation of oocytes of all females.