Effects Of Dehydroepiandrosterone On Biological Transformation And Its Mechanism In Female Rats

Dehydroepiandrosterone (DHEA) is the most important intermediate metabolites of cholesterol, have an important effect in regulating animal various physiological functions. In previous results indicated that the serum contents of circulating sex steroid hormones and their metabolites, the expression of the steroidogenesis-related enzymes significantly increased after DHEA administration in adult and aged male rats, especially the contents of testosterone and estradiol in serum. But the bioconversion of DHEA in gonad tissue of female adult animals is not clear. Ovary is the main endocrine organ of steroid hormones in female adult animal, sex hormones were mainly synthesised by granulose and membrane cells of the follicle. These given rise to the widespread attention of DHEA in the physiological function, especially the effect in the female endocrine and maintaining a healthy state. Many researchers showed that the biological function of DHEA mainly attributed to its intermediate/final metabolites in vivo. But the characteristics of biological transformation and major target tissue of DHEA were no distinct. So in the present study, we have used normal and ovariectomised female rats as models to analysis that how DHEA affects the content of circulating steroid hormones and their metabolites, the expression levels of steroidogenesis-related enzymes mRNA and their trade-off relationship; Granulose cells were released by mechanical method as the specific target cell to study the biological transformation and the change of steroidogenesis-related enzymes expression, aims to reveal the pattern and detail of biotransformation of DHEA in female rats, in order to promote animal health care and provide theoretical basis for the prevent and control related diseases.1 Effect of dehydroepiandrosterone (DHEA) on steroid hormones and the expression of steroidogenic enzymes in normal ratsThe study use the normal female rats as model to investigate that the effect of dehydroepiandrosterone (DHEA) on circulating steroid hormones and the expression levels of steroidogenesis-related enzymes mRNA in adrenal and ovary. In this study,70 healthy adult female Sprague-Dawley (SD) rats were randomly divided into control and 25mg-kg-1 DHEA-treated groups. The animals were sacrificed at 0,3,6,12,24 and 48 h. All the samples were collected for subsequent analysis. Results showed that compare the control, the androstenedione and testosterone concentrations markedly increased after DHEA administration over 3-12 h(P<0.01), decreased during the next 24-48 h(P<0.05), the maximal serum concentrations of androstenedione in the DHEA-treated group, which occurred at 3 h, increased by 165%; The testosterone concentrations markedly increased after DHEA administration over 3-6 h(P<0.01), the maximal serum concentrations of testosterone occurred at 3 h, showed a 8000% decrease above control levels. On the other hand,the serum concentration of estradiol significantly increased only at 6 h (P<0.01), and reached the maximum value, was 113% above control at the same time interval; however estrone and progesterone levels did not change statistically’significantly over the 48 h period. Compare the control, DHEA administration cause a significant increases of the cortisol concentration at 3 h, but decreased again at 24 h (P<0.05), aldosterone was significantly increased just at 6 h (P<0.05). The change of steroidogenesis-related enzymes mRNA The results showed that oral administration of DHEA, the expression of the 3β-HSD mRNA significantly reduced over a 12 h period in ovary of normal female rats (P<0.05), and the 17β-HSD mRNA expression levels significantly decreased in ovary only at 12 h relative to the other time points (P<0.01). Aromatase mRNA expression level also significantly decreased at 3 h and 12 h (P<0.01), while a dramatic up regulation occurred at 6 h,24 h and 48 h in ovary of normal female rats (P<0.01). It is interesting that the oral administration of DHEA caused a significant increase of 17β-HSD,3β-HSD and aromatase mRNA expression over a 12 h period in adrenal of normal female rats (P<0.05), but no noticeable change of aromatase mRNA expression at 6 h after DHEA administration (P>0.05).These results clearly illustrated that DHEA administration to normal adult female rats lead to a markedly increase of androgens(androstenedione and testosterone) concentrations in serum, estrogens (estradiol) and adrenocortical hormone(cortisol and aldosterone); Transformation of exogenous DHEA in normal adult female rats is preferentially into androgens rather than into estrogens; The conversion of DHEA to androgens depends on increasing the expression of 3β-HSD、17β-HSD mRNA in adrenal, the conversion of DHEA to estrogens mainly depend on increasing the expression of Aromatase mRNA in ovary.2 Effect of dehydroepiandrosterone (DHEA) on steroid hormones and the expression of steroidogenic enzymes in ovariectomised (OVX) ratsThe study use the ovariectomised rats as model to investigate that the effect of dehydroepiandrosterone (DHEA) on circulating steroid hormones and the expression levels of steroidogenesis-related enzymes mRNA in adrenal. In this study,30 healthy adult female Sprague Dawley (SD) rats were randomly divided into three groups:Sham-operated (SO), Ovariectomised (OVX) and Ovariectomy+DHEA treatment. The animals were sacrificed at 6h.All the samples were collected for subsequent analysis. Results showed that compared with SO, the serum level of androstenedione, testosterone, were reduced 48,25% in the OVX-control (P>0.05). However, compared with OVX-control, the androstenedione, testosterone concentrations were markedly increased 1296% and 11250% in OVX +DHEA(P<0.01), respectively; Compared with SO, the serum level of estradiol, estrone, progesterone significantly were reduce 46%,73% and 58% in the OVX-control(P<0.05). However, compared with OVX-control, the levels of estradiol, estrone, progesterone in serum showed a more moderate increase after DHEA administration (P>0.05); Compared with SO; the serum levels of cortisol, adosterone did not change significantly in the OVX-control (P>0.05); Also, no significant difference was observed for cortisol, adosterone after DHEA administration (P>0.05). The change of steroidogenesis-related enzymes mRNA No significant difference were observed in the expression levels of 17β-HSD and aromatase mRNA between SO and OVX-control groups, while there was a significant increase in the expression of 3β-HSD mRNA after the ovarian removed in the OVX-control (P<0.05). Compared with OVX-control, the expression of the adrenal steroidogenic enzymes including 3β-HSD (P<0.01) and 17β-HSD (P<0.05) mRNA significantly elevated after DHEA administration in ovariectomised rats. While the expression level of aromatase mRNA, on the other hand, showed a significant decrease after DHEA administration than that of the OVX-control group (P<0.05).These results clearly illustrated that DHEA administration to ovariectomised rats lead to a markedly increase of the androstenedione and testosterone in serum, had no effect on the estrogens (estradiol、estrone、progesterone) and adrenocortical hormone(cortisol and aldosterone) contents; The conversion of DHEA to androgens depend on increasing the expression of 3β-HSD.17β-HSD mRNA and reducing the expression of Aromatase mRNA in adrenal.3 Effect of dehydroepiandrosterone (DHEA) on steroid hormones and the expression of steroidogenic enzymes in rat primary granulose cellsThe study use the rat primary granulose cells as model to investigate that the effect of dehydroepiandrosterone (DHEA) on circulating steroid hormones and the expression levels of steroidogenesis-related enzymes mRNA. Granulose cells were released by mechanical method. The culture media at 48h after treatment were collected for the measurements of progesterone、estradiol、testosterone level with RIA. The expression of 3β-HSD、17β-HSD and Aromatase mRNA in the cultured granulose cells were detected by RT-PCR. Results showed that estradiol levels in medium rised gradually as DHEA concentration increased, markedly elevated in 10μmol/L (P<0.01). The levels of serum progesterone and testosterone also markly increased after 10μmol/L (P<0.01) of DHEA administration. DHEA administration canused a markly increase of the expression of 3β-HSD(P<0.01)、 17β-HSD (P<0.05) mRNA, but not statistically significant increase in the expression of Aromatase mRNA as compared to the control. The results indicated that DHEA may interrupt steroidogenesis by acting on the expression levels of steroidogenesis-related enzymes mRNA.