阉割和睾丸酮替代对雄性老年大鼠下丘脑和血浆促黄体生成素释放激素水平的影响

EFFECTS OF CASTRATION AND TESTOSTERONE-REPLACEMENT ON HYPOTHALAMIC AND PLASMA LUTEINIZING HORMONE-RELEASING HORMONE LEVELS IN THE AGED MALE RAT

应用放射免疫分析(RIA)技术比较了年青(2—3月龄)和老年(24—26月龄)雄性大鼠下丘脑和血浆促黄体生成素释放激素(LHRH)水平及其在睾丸切除(ORDX)和睾丸酮(T)替代下LHRH水平的变化。老年大鼠血浆T水平明显降低,下丘脑LHRH含量亦呈明显下降趋势,但血浆LHRH水平与年青大鼠十分接近。在ORDX和T替代下,两组动物血浆T水平没有明显差别,但老年大鼠下丘脑和血浆LHRH的变化率却不同程度地低于年青大鼠。上述结果提示,老年雄性大鼠下丘脑LHRH神经元系统的负反馈能力明显削弱,这也许是下丘脑-垂体-睾丸轴呈增龄性衰变的重要原因之一。

Hypothalamic and plasma luteinizing hormone-releasing hormone (LHRHlevels following orchidectomy (ORDX) and testosterone (T)-replacement were com-pared between young (2--3 months old) and aged (24--26 months old) male ratsby radioimmunoassay. Plasma T level and hypothalamic LHRH content aremarkedly decreased in the aged rat as compared to those of the young rat, whereasplasma LHRH levels are similar in the two groups. Followng ORDX and ORDXplus T-replacement, plasma T levels in both groups are about the same, whereasthe rates of variation of hypothalamic and plasma LHRH levels in the aged ratare significantly lower than those in the young rat. These results suggest that thenegative feedback mechanism of the hypothalamic LHRHergic system is impairedin the aged rat, which may be one of the important reasons causing age-dependentdeterioration of the functional control of hypothalamic-pituitary-testicular axis.