Negri-Cesi P, Celotti F, Melcangi R C, Martini L
J Steroid Biochem. 1987 Aug;28(2):179-84. doi: 10.1016/0022-4731(87)90374-8.
It is known that the metabolism of testosterone in the brain and in the anterior pituitary is different in mammalian and in photoperiodic avian species. In many mammalian species, testosterone is mainly metabolized to 5-alpha-reduced compounds (e.g. 17-beta-hydroxy-5-alpha-androstan- 3-one, 5 alpha-DHT and 3-alpha,17-beta-dihydroxy-5-alpha-androstane, 5-alpha,3-alpha-diol) and, to a smaller extent, to 4-androstene-3,17-dione (androstenedione), while in birds, androstenedione is the main testosterone metabolite and the conversion to the 5-alpha-reduced compounds is quantitatively negligible. In avian species, testosterone is also converted to 5-beta-reduced steroids (mainly 17-beta-hydroxy-5-beta-androstan-3-one, 5-beta-DHT and 3-alpha,17-beta-dihydroxy-5-beta-androstane, 5-beta,3-alpha-diol), and there is also evidence that in these species testosterone metabolism in the central structures may be influenced by the photoperiod. Since the hamster is a mammal whose reproductive cycle is controlled by day length, it has been analyzed whether: (a) the central structures of the hamster (cerebral cortex, hypothalamus and anterior pituitary) metabolize testosterone in vitro following a mammalian (5-alpha-reduced derivatives) or an avian (androstenedione and 5-beta-reduced compounds) pattern; and (b) the metabolism of testosterone in the same structures may be modified by the exposure to different photoperiods (LD 14:10 or LD 8:16). The present data indicate that no one of the hamster structures examined produces the 5-beta-reduced derivatives. Moreover, the formation of the 5 alpha-DHT is quantitatively low, and is not affected by the photoperiod. In contrast, androstenedione is formed in quite high yields and the exposure of the animals to 60 days of short photostimulation increases the formation of this steroid in the pituitary gland, but not in the brain structures. From these data, it appears that the central structures of the hamster metabolize testosterone with a pattern which is intermediate between that of birds and mammals.
已知在哺乳动物和光周期鸟类中，大脑和垂体前叶中睾酮的代谢情况不同。在许多哺乳动物物种中，睾酮主要代谢为5-α还原化合物（如17-β-羟基-5-α-雄甾烷-3-酮、5α-DHT和3-α,17-β-二羟基-5-α-雄甾烷、5-α,3-α-二醇），在较小程度上代谢为4-雄烯-3,17-二酮（雄烯二酮），而在鸟类中，雄烯二酮是睾酮的主要代谢产物，向5-α还原化合物的转化在数量上可忽略不计。在鸟类物种中，睾酮还会转化为5-β还原类固醇（主要是17-β-羟基-5-β-雄甾烷-3-酮、5-β-DHT和3-α,17-β-二羟基-5-β-雄甾烷、5-β,3-α-二醇），并且也有证据表明在这些物种中，中枢结构中的睾酮代谢可能受光周期影响。由于仓鼠是一种繁殖周期受日长控制的哺乳动物，因此分析了：（a）仓鼠的中枢结构（大脑皮层、下丘脑和垂体前叶）在体外是否按照哺乳动物模式（5-α还原衍生物）或鸟类模式（雄烯二酮和5-β还原化合物）代谢睾酮；以及（b）相同结构中睾酮的代谢是否会因暴露于不同光周期（LD 14:10或LD 8:16）而改变。目前的数据表明，所检测的仓鼠结构中没有一个会产生5-β还原衍生物。此外，5α-DHT的形成量在数量上较低，且不受光周期影响。相反，雄烯二酮的形成量相当高，将动物暴露于60天的短光照刺激下会增加垂体中这种类固醇的形成，但不会增加脑结构中的形成量。从这些数据来看，仓鼠的中枢结构代谢睾酮的模式介于鸟类和哺乳动物之间。
