Takahashi S, Nomura K, Kawashima S
Zoological Institute, Faculty of Science, Hiroshima University, Japan.
Endocrinol Jpn. 1990 Apr;37(2):213-21. doi: 10.1507/endocrj1954.37.213.
Age-related changes in hypothalamic luteinizing hormone-releasing hormone (LHRH) and luteinizing hormone (LH) secretion were studied in young (6 months), middle-aged (12 months) and old (18 months) female rats. The LHRH levels in the mid-hypothalamic area were higher in intact middle-aged and old females than in young ones. Additionally, there was no age difference in the hypothalamic LHRH levels in male rats. In order to clarify the significance of this age-related increase in female rats, we examined the effects of progesterone treatment in estrogen-primed ovariectomized young and old rats on the LHRH levels in the median eminence (ME) and on plasma LH levels. We found phasic changes in ME-LHRH and plasma LH levels in estrogen-primed rats following progesterone treatment in rats of both ages, but the progesterone-induced change in ME-LHRH levels tended to be delayed in old rats compared with young females. This delay may correspond to the delayed onset, slow and low magnitude of plasma LH increase in old females. The ME-LHRH levels were generally higher in old rats than in young rats. Nevertheless, we found that the increase in plasma LH in response to progesterone treatment in estrogen-primed ovariectomized females was smaller in old rats than young rats. These results suggest that the LHRH secretory mechanism changes with age in female rats. Such alterations may result in the accumulation of LHRH in the mid-hypothalamic area and an increase in ME-LHRH.
研究了年轻（6个月）、中年（12个月）和老年（18个月）雌性大鼠下丘脑促黄体生成激素释放激素（LHRH）和促黄体生成激素（LH）分泌的年龄相关变化。完整的中年和老年雌性大鼠下丘脑中部区域的LHRH水平高于年轻大鼠。此外，雄性大鼠下丘脑LHRH水平不存在年龄差异。为了阐明雌性大鼠这种与年龄相关的增加的意义，我们研究了对雌激素预处理的去卵巢年轻和老年大鼠进行孕酮处理对正中隆起（ME）中LHRH水平和血浆LH水平的影响。我们发现，在两个年龄段的大鼠中，孕酮处理后，雌激素预处理大鼠的ME-LHRH和血浆LH水平出现阶段性变化，但与年轻雌性大鼠相比，老年大鼠中孕酮诱导的ME-LHRH水平变化往往延迟。这种延迟可能与老年雌性大鼠血浆LH升高的起始延迟、缓慢且幅度较低相对应。老年大鼠的ME-LHRH水平通常高于年轻大鼠。然而，我们发现，雌激素预处理的去卵巢雌性大鼠中，孕酮处理后老年大鼠血浆LH的增加幅度小于年轻大鼠。这些结果表明，雌性大鼠的LHRH分泌机制随年龄变化。这种改变可能导致LHRH在下丘脑中部区域积累以及ME-LHRH增加。
