Wójtowicz A K, Goch M, Gregoraszczuk E L
Laboratory of Physiology and Toxicology of Reproduction, Department of Animal Physiology, Institute of Zoology, Jagiellonian University, Kraków, Poland.
Exp Clin Endocrinol Diabetes. 2005 Sep;113(8):464-70. doi: 10.1055/s-2005-865776.
To look for one of the possible mechanisms of action we investigated the effect of two congeners of polychlorinated biphenyls (PCB153 as one of the most prominent environmental contaminants and PCB 126 as one of the most toxic contaminants similar to dioxin) on the cellular conversion of steroid precursors as an indicator for enzyme activity (20-hydroxylated cholesterol to progesterone for P450 (scc,) androstendione to testosterone for 17-beta-HSD, and testosterone to estradiol for P450 (arom)). The net synthesis and secretion of particular steroids was used as the indicator of enzyme activity. Co-culture of pig granulosa and theca cells isolated from small (SF) and large (LF) follicles, was carried out in medium M199 supplemented with 100 ng/ml of PCB 153 or 100 pg/ml of PCB 126. The inhibitory action of both PCB 126 and PCB 153 on progesterone secretion by cells isolated from SF and LF follicles was reversed in the presence of 20-hydroxylated cholesterol. The addition of PCB 126 into the culture medium caused a decrease in testosterone secretion by cells isolated from both SF and LF and this effect was reversed in the presence of androstendione. The inhibitory action of PCB 153 on testosterone secretion was reversed by the addition of androstendione to the culture medium in SF, while it caused even additional stimulatory action on cells collected from LF. No effect of PCB 126 and statistically significant decrease in estradiol secretion by cells collected from SF under the influence of PCB153 was observed. The inhibitory effect of PCB 153 was reversed when the culture was supplemented with testosterone. The opposite effect of both tested congeners on estradiol secretion in both basal and testosterone supplemented culture was seen in LF. PCB 126 increased it while PCB 153 decreased both, the basal and testosterone-stimulated estradiol secretion. In conclusion, the presented results suggest that the effect of both PCBs on steroid secretion observed in an early stage of the follicular phase of the estrus cycle is due to the inhibition of cholesterol mobilisation and thus insufficient substrate availability for hormone synthesis. On the contrary, in large preovulatory follicles inhibition of testosterone secretion is due to their action on 17-beta-HSD while stimulatory or inhibitory action on estradiol secretion is the result of their action on P450 aromatase activity.
为了探寻可能的作用机制之一，我们研究了两种多氯联苯同系物（作为最突出的环境污染物之一的多氯联苯153和作为与二噁英相似的毒性最强的污染物之一的多氯联苯126）对类固醇前体细胞转化的影响，以此作为酶活性的指标（20-羟基胆固醇转化为孕酮用于检测P450（侧链裂解酶），雄烯二酮转化为睾酮用于检测17-β-羟类固醇脱氢酶，睾酮转化为雌二醇用于检测P450（芳香化酶））。特定类固醇的净合成和分泌用作酶活性的指标。从小型（SF）和大型（LF）卵泡分离的猪颗粒细胞和卵泡膜细胞在添加了100 ng/ml多氯联苯153或100 pg/ml多氯联苯126的M199培养基中进行共培养。在存在20-羟基胆固醇的情况下，多氯联苯126和多氯联苯153对从SF和LF卵泡分离的细胞分泌孕酮的抑制作用被逆转。向培养基中添加多氯联苯126导致从SF和LF分离的细胞分泌睾酮减少，而在存在雄烯二酮的情况下这种作用被逆转。在SF中，向培养基中添加雄烯二酮可逆转多氯联苯153对睾酮分泌的抑制作用，而它对从LF收集的细胞甚至产生额外刺激作用。未观察到多氯联苯126的作用以及在多氯联苯153影响下从SF收集的细胞分泌雌二醇有统计学意义的显著降低。当培养基中添加睾酮时，多氯联苯153的抑制作用被逆转。在LF中，两种受试同系物对基础培养和添加睾酮培养中的雌二醇分泌均产生相反作用。多氯联苯126使其增加，而多氯联苯153则降低基础分泌和睾酮刺激的雌二醇分泌。总之，呈现的结果表明，在发情周期卵泡期早期观察到的两种多氯联苯对类固醇分泌的影响是由于胆固醇转运受到抑制，从而激素合成的底物供应不足。相反，在大型排卵前卵泡中，睾酮分泌受到抑制是由于它们对17-β-羟类固醇脱氢酶的作用，而对雌二醇分泌的刺激或抑制作用是它们对P450芳香化酶活性作用的结果。
