Effect And Mechanism Of Cadmium On The Progesterone Synthesis Of Ovaries

ObjectiveThe paper presents results of the effect of cadmium on the progesterone synthesis of ovaries.To study the effect and its mechanism steroidogenic acute regulatory protein (StAR)and the cytochrome P450 side chain cleavage (P450scc) of rat following cadmium exposures in vivo (at 2.5,5,7.5mg/kg,as a single s.c. dose) and in vitro (0,10,20,40μM), ovaries granule cells were used.Methods1. 48 hours after the pregnant mare serum gonadotropin (PMSG) was administrated subcutaneously at the dose of 100 IU to Wistar rats. The ovaries granule cells were took out and incubated in Dulbecco modified Eagle medium (DMEM)- F12 for the following study. Cultures of ovaries granule cells of rat were exposured to Cadmium (CdCl2) at the different concentrations of 0,10,20,40μM respectively (The sample of every group was 12 ). Progestone (P4) and cAMP were determinated with radioimmunoassay (RIA) following 30 minutes exposured, StAR and P450scc mRNA were determinated by RT-PCR.2. The ovaries granule cells were prepared and cultured in DMEM- F12.(The method was the same with above ). The ovaries granule cells were randomly assigned to three groups: 40μMCdCl2,40μMCdCl2+1mM8-Br-cAMP and controls, coclutured for 2 hours (The sample of every group was 12 ). P4 was determinated with RIA, and StAR and P450scc mRNA were determinated by RT-PCR.3. Fourty-eight mature Wistar rats were weight and randomly assigned to four groups based on body weight and were exposed to CdCl2 at 2.5,5,7.5mg/kg,as a single s.c. dose. The serum P4 and P4 of ovaries granule cells were mearsured after 24 hours by RIA, population of ovaries granule cells were detected, the expression of StAR and P450scc were determinated with RT-PCR.Results1.①In- vitro cadmium exposure interfered with normal steroidogenesis in ovaries granule cells. As the concentrations of CdCl2 were increased, progesterone levels were significantly declined in a dose-dependent manner in granule cells (P<0.01). The concentations of cAMP in the 40μM and 20μM groups were significantly lower than other groups (P<0.01). The expression of StAR in each group were significantly lower than control group(P<0.05), and The expression of P450scc in each group were significantly lower than control group(P<0.01).②The P4 level in the 1mM 8- Br -cAMP +40μM CdCl2 group was significantly higher than that in 40μMCdCl2 group(P<0.01). The expression of StARmRNA in 40μM were significantly lower than control groups (P<0.01), The expression of StARmRNA in 8- Br -cAMP +40μM CdCl2 were significantly higher than 40μM CdCl2,and were significantly lower than control group(P<0.01); The expression of P450scc mRNA in 40μM were significantly lower than control groups (P<0.01), the rate was 30%; The expression of P450scc mRNA in 8- Br -cAMP +40μM CdCl2 were significantly higher than 40μM CdCl2,and were significantly lower than control group(P<0.01).2. In- vivo, The serum P4 in cadmium exposure group were significantly lower than control group(P<0.01). The P4 of granule cells in 7.5mg/kg were significantly lower than control group(P<0.01). The expression of StAR mRNA in 5 mg/kg and 7.5mg/kg were were significantly lower than control group(P<0.01). Population of ovaries granule cells in 7.5mg/kg were significantly lower than control group(P<0.05), and as the concentrations of CdCl2 were increased, cell population were declined ,but it was no significantly (P>0.05). The expression of P450scc mRNA in each group were significantly lower than control group(P<0.01).Conclusions ①There were the effects of cadmium that may depress the level of P4 of ovaries granule cells and serum P4, which is one of important mechanism of progesterone dyssynthesis.②The reduction in the expression of StAR and P450scc mRNA in the progesterone synthesis of ovaries have been shown, and which is considered as important mechanism of endocrine disruption.③In this experiment, the concentrations of cAMP in ovaries granule cells have been reduced down with the exposure of cadmium. And also, it has been shown that the expression of StAR and P450scc mRNA can been regulated by cAMP, which suggested that cadmium interfere progesterone biosynthesis by inhibition of cAMP .④The result suggested that in the effect and mechanism of cadmium on progesterone synthesis of ovaries, the effect of hypothalamic-pituitary-ovarian axis(HPOA) was poor. Or progesterone pathway was interfered directly with the exposure of cadmium.