褪黑素对SD大鼠下丘脑-垂体-肾上腺皮质的影响

目的 研究褪黑素对正常和糖尿病大鼠下丘脑-垂体-肾上腺皮质功能和超微结构的影响.方法 应用放射免疫法分别观察了低、中、高剂量(0.5mg/kg、10mg/kg、50mg/kg)褪黑素及对照药物硫辛酸(100mg/kg)连续腹腔注射3周,对SD大鼠血浆促肾上腺皮质激素释放激素(CRH)、促肾上腺皮质激素(ACTH)、皮质酮(COR)水平的影响.并运用电镜观察用药前后大鼠垂体、肾上腺皮质超微结构的变化.结果 1.正常和糖尿病大鼠低、中、高剂量褪黑素处理组CRH水平与相应对照组相比显著降低;正常大鼠低、中、高剂量褪黑素及硫辛酸处理组和糖尿病大鼠低剂量(0.5mg/kg)褪黑素、硫辛酸处理组ACTH水平比相应对照组明显降低(P＜0.05);正常大鼠低、中、高剂量褪黑素处理组和糖尿病大鼠中高剂量褪黑素处理组皮质酮水平比相应对照组显著降低(P＜0.05).2.褪黑素对正常大鼠下丘脑-垂体-肾上腺皮质超微结构无明显影响.糖尿病大鼠垂体细胞和肾上腺皮质细胞出现功能受抑制状态,褪黑素(50mg/(kg·d))处理21d后垂体促肾上腺皮质细胞和肾上腺皮质细胞代谢较处理前明显活跃.结论 褪黑素能在不同层次直接或间接地发挥对正常和糖尿病大鼠下丘脑-垂体-肾上腺(HPA)轴的抑制作用.

EFFECTS OF MELATONIN ON HPA AXIS IN RATS

Objective To study the functional and ultramicrostructural effects of melatonin on hypothalamus-pituitary-adrenal(HPA) axis in normal and diabetic rats.Methods By means of radioimmunoassay we observed the effects of three doses of melatonin(0.5mg/kg for low,10mg/kg for medium,50mg/kg for high) and lipoicin on level of CRH,ACTH and COR in normal and diabetic rats' plasma for three weeks respectively.The ultramicrostructural changes of hypophysis and pituitary gland after melatonin treatment were also observed under transmission electron microscope(TEM).Results 1.Compared with control groups,the CRH level of melatonin groups in normal and diabetic rats notably reduced(P<0.05).ACTH level of three doses of melatonin and lipoicin treatment groups in normal rats decreased,while medium-dose-melatonin and lipoicin group in diabetic rats markedly fell(P<0.05).COR level turned out the same result with CRH level in normal rats,whereas CRH level in high and medium doses melatonin treated groups of diabetic rats had a significantly reduction trend.2.The melatonin treatment to normal rats had no apparent effect on the ultramicrostructures of hypophysis and pituitary gland cells,but the hypophysis and pituitary gland tissues were targets of diabetic lesion with low metabolism functions.However,our morphological study demonstrated that the melatonin treatment might obviously strengthen the hypophysis and pituitary gland cell metabolism function in resisting the response with diabetic oxidative stress.Conclusion Melatonin can exert inhibition to HPA axis of normal and diabetic rats in various levels directly or indirectly.