Pirke K M, Krings B, Vogt H J
Acta Endocrinol (Copenh). 1979 Oct;92(2):358-69. doi: 10.1530/acta.0.0920358.
The dysfunction of the hypothalamic-pituitary-gonadal axis in old age was studied in 24-month old male Wistar rats which were compared with 3-month old animals. The hypothalamic LH-RH content and the pituitary LH were significantly lower in the old than in the young adult animals. The plasma concentrations of LH and testosterone were significantly higher in the young rats. The primary cause of these age-dependent changes probably is a hypothalamic dysfunction. When isolated Leydig cells of young and old rats were incubated in vitro, the testosterone secretion per cell was significantly smaller in old than in young cells with as well as without HCG stimulation. In vivo stimulation of rats by iv injection of biologically active iodinated hCG revealed that the intratesticular uptake of the gonadotrophin was not different in young and old rats. The testosterone response, however, was significantly reduced in old age. An in vitro "desensitisation" experiment in which the LH receptor capacity was artificially reduced demonstrated that the 40% reduction of receptor capacity in old testes as described earlier will not impair the testicular uptake of gonadotrophin from blood. Repeated injection of hCG results in equally elevated testosterone concentrations in young and old rats.
对24月龄雄性Wistar大鼠的下丘脑 - 垂体 - 性腺轴功能障碍进行了研究，并与3月龄动物进行比较。老年大鼠下丘脑促黄体激素释放激素（LH - RH）含量和垂体促黄体激素（LH）显著低于年轻成年动物。年轻大鼠血浆中LH和睾酮浓度显著更高。这些与年龄相关变化的主要原因可能是下丘脑功能障碍。当将年轻和老年大鼠的分离睾丸间质细胞进行体外培养时，无论有无人绒毛膜促性腺激素（HCG）刺激，老年细胞每细胞的睾酮分泌均显著少于年轻细胞。通过静脉注射生物活性碘化HCG对大鼠进行体内刺激显示，年轻和老年大鼠促性腺激素的睾丸内摄取没有差异。然而，老年大鼠的睾酮反应显著降低。一项体外“脱敏”实验，其中人为降低LH受体容量，结果表明，如前所述老年睾丸中受体容量降低40%不会损害睾丸从血液中摄取促性腺激素。重复注射HCG会使年轻和老年大鼠的睾酮浓度同样升高。
