Blouquit M F, Valens M, Bagayoko A, Gripois D
Laboratoire d'Endocrinologie, Université Paris-Sud, Orsay, France.
J Dev Physiol. 1990 Dec;14(6):325-9.
Adrenal tyrosine hydroxylase activation was elicited in developing control, hypo- and hyperthyroid rats by insulin-hypoglycaemia. Rats were deeply anaesthetized with chloroform at a low concentration, since intrinsic tyrosine hydroxylase activation was very low with this technique, as compared to Ketamine injection or chloroform at a high concentration. The study of time-course of tyrosine hydroxylase activation showed that the maximum value was observed 2 h after insulin administration. In control animals, tyrosine hydroxylase activation increased between 4 and 20 days, and then decreased. Hypothyroidism is associated with a decreased tyrosine hydroxylase activation between 4 and 50 days, as compared to controls and hyperthyroidism with an increased activation between 6 and 30 days. While tyrosine hydroxylase from saline-treated rats exhibits two different forms (with two apparent Km values for the cofactor), enzyme from insulin-treated animals was present in a single form with a Km corresponding to the low Km value of the saline-injected rats. At 6 and 14 days, hypothyroidism increases tyrosine hydroxylase Km values as compared to euthyroid animals.
通过胰岛素低血糖法在发育中的对照、甲状腺功能减退和甲状腺功能亢进大鼠中引发肾上腺酪氨酸羟化酶激活。由于与氯胺酮注射或高浓度氯仿相比，采用这种技术时内在的酪氨酸羟化酶激活非常低，所以用低浓度氯仿将大鼠深度麻醉。酪氨酸羟化酶激活的时间进程研究表明，胰岛素给药后2小时观察到最大值。在对照动物中，酪氨酸羟化酶激活在4至20天之间增加，然后下降。与对照组相比，甲状腺功能减退与4至50天之间酪氨酸羟化酶激活降低有关，而甲状腺功能亢进与6至30天之间激活增加有关。虽然用生理盐水处理的大鼠的酪氨酸羟化酶表现出两种不同形式（对辅因子有两个表观Km值），但用胰岛素处理的动物的酶以单一形式存在，其Km对应于注射生理盐水的大鼠的低Km值。与甲状腺功能正常的动物相比，在6天和14天时，甲状腺功能减退会增加酪氨酸羟化酶的Km值。
