糖皮质激素通路介导邻苯二甲酸二丁酯对大鼠睾酮合成的抑制作用

目的 探讨邻苯二甲酸二丁酯(DBP)抑制大鼠睾酮(T)合成的作用机制.方法 雄性Wistar大鼠按数字表法随机分为5组,即0.25、0.50、1.00和2.00g/kg DBP剂量组和溶剂对照组,每组16只.经口灌胃,每天1次,连续30 d,染毒结束后,每组处死8只动物,另8只饲养15 d后处死.放射免疫法检测血清T和糖皮质激素(GC)水平;RT-PCR法检测11 β-羟类固醇脱氢酶(11β-HSD)和类固醇生成急性调控蛋白(StAR)基因表达水平;Western blotting检测糖皮质激素受体(GR)表达水平.结果 染毒期,1.00和2.00 g/kg DBP剂量组血清T水平分别为(0.260±0.218)和(0.260±0.342)ng/ml,GC水平分别为(13.470±5.661)和(13.740±3.977)ng/ml,对照组血清T水平为(1.045±1.222)ng/ml,GC水平为(9.224±3.496)ng/ml,1.00和2.00g/kg DBP剂量组与对照组比较,差异有统计学意义(tT值分别为-2.295、-2.295,tGC值分别为2.159和2.296,P值均小于0.05);1.00和2.00 g/kg DBP剂量组StAR基因表达水平降低,STAR/β-Actin比值分别为0.657±0.060和0.407±0.033,与对照组(0.871±0.081)比较,差异有统计学意义(t值分别为-3.707和-8.037,P值均小于0.05);1.00和2.00 g/kg DBP剂量组11β-HSD基因表达水平(11β-HSD/β-Actin比值分别为0.538±0.138和0.988±0.133)和GR蛋白表达水平(GR/β-Actin比值分别为0.785±0.106和0.956±0.076)与对照组(0.285±0.106和0.275±0.035)比较,差异有统计学意义(t11β-HSD/β-Actin值分别为2.829、7.860,tGR/β-Actin值分别为8.064和10.77,P值均小于0.05),与DBP剂量呈正相关,r值分别为0.776和0.790.恢复期,DBP各剂量组上述指标与对照组比较差异均无统计学意义.结论 DBP能通过GC通路介导对大鼠T合成的抑制作用.

Glucocorticoid pathway mediated the inhibition of testosterone in rats exposed to dibutyl phthalate

Objective To investigate the inhibitory mechanisms of testosterone (T) biosynthesis in rats exposed to dibutyl phthalate (DBP). Methods Male Wistar rars were randomly divided into five groups by weight, including 0. 25,0. 50,1.00,2. 00 g/kg DBP groups and com oil control group, with 16 rats in each group. DBP was administered by garage once a day. After 30 days exposure,eight mrs in each group were killed and the others were killed after 15 days without DBP administration. The levels of T and glueocorticoid (GC) in serum were determined by radioimmunoassay. The expression levels of 11 beta-dedroxysteriod dehydrogenase (1β-HSD) mRNA and steroidogenesis acuteregulatory protein (StAR) mRNA were determined by RT-PCR. The protein expression level of glucocorticoid receptor (GR) was investigated by Western blotting. Results During exposure period,in 1.00 and 2. 00 g/kg DBP groups,the levels of T were (0.260±0.218) ng/ml and (0.260±0. 342) ng/ml,the levels of GC were (13.470±5. 661) ng/ml and (13. 740±3.977)ng/ml ,the levels of T and GC in control group were (1.045±1.222) ng/ml and (9. 224±3. 496) ng/ml. There were statistic differences between 1. 00 and 2. 00 g/kg DBP groups and control group (tT values were-2. 295 and-2. 295, tGC values were 2. 159 and 2. 296, respectively,P<0. 05). The expression level of StAR mRNA was significantly down-regulated in 1.00 and 2.00 g/kg DBP groups, while StAR/β-Actin values were 0. 657±0. 060 and 0. 407±0. 033, and compared to control group (0. 871±0. 081), there was statistic difference (t values were-3. 707 and-8. 037 ,P <0. 05). In 1.00 and 2. 00 g/kg DBP groups, the expression of 11β-HSD mRNA and the expression of GR protein were increased in DBP dose-dependent manner,while 11β-HSD/β-Actin values were 0. 538±0. 138 and 0. 988±0. 133, and GR/β-Actin were 0. 785±0. 106 and 0. 956±0. 076, respectivdy. There were statistic difference,as compared to the controls (0. 285±0. 106 and 0. 275±0. 035) (t11β-HSD/β-Actin values were 2. 829 and 7. 860, tGR/βAction values were 8. 064 and 10. 77, respectively, P<0. 05). Linear correlation and regression revealed that there were positive correlation between DBP dose and the expression levels of 11β-HSD mRNA and GR protein, with r values of 0. 766 and 0. 790, respectively. In post-exposure period, there were no statistic differences of all above index among DBP groups and control group. Conclusion DBP might inhibit T production in rats through GR mediation.