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M. HIROI, K. STEVENS and R. GORSKI

Summary.

In normal cyclic female rats, an injection of 16 mg CuSO4/kg induces pseudopregnancy (as determined by uterine traumatization) when given on the day of oestrus, or on the following day. Pentobarbital anaesthesia did not inhibit this effect of CuSO4. Pseudopregnancy, as determined by inhibition of the induction of vaginal cornification by exogenous oestrogen, was also induced by CuSO4 in anovulatory females, provided the injection was given from 6 hr before, to 24 hr after injection of human chorionic gonadotrophin. The latter was necessary since CuSO4 did not induce ovulation in forty experimentally produced anovulatory rats. Cupric sulphate injected on the day of vaginal pro-oestrus in normal females did not alter the incidence of spontaneous ovulation nor the number of ova shed. These data suggest an effect of copper ion in the rat on luteal regulatory mechanisms rather than on ovulatory mechanisms; the site of action cannot, however, be specified.

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Y. Shiina, M. Kaneda, K. Matsuyama, K. Tanaka, M. Hiroi and K. Doi

Changes in intracellular calcium concentration ([Ca2+]i) in fertilized mouse oocytes were measured using the calcium-sensitive dye, fura-2. After fertilization, an initial long-lasting [Ca2+]i increase was followed by a periodic [Ca2+]i increase. The periodic increase in [Ca2+]i persisted for 1 to 3 h and all fertilized oocytes extruded the second polar body within 4 h. The mean interval of periodic [Ca2+]i increase was 470 ± 180 s (mean ± sd). The frequency of the periodic [Ca2+]i increase depended on the extracellular calcium concentration. Verapamil and nifedipine inhibited the periodic [Ca2+]i increase. Sixty-five per cent of tested cells extruded the second polar body within 90 min of exposure to 7% ethanol. In these activated oocytes, the long-lasting [Ca2+]i increase was observed. However, no cells showed a repetitive increase in [Ca2+]i Both release of calcium from intracellular stores and influx of extracellular calcium contribute to the increase in [Ca2+]i induced by ethanol. We conclude that the extrusion of the second polar body requires an increase in [Ca2+]i above a certain threshold level and the mobilization of calcium of both the intracellular and extracellular space in mouse oocytes.