Induction of Tyrosine Hydroxylase in Peripheral and Central Adrenergic Neurones by Cold-exposure of Rats
Induction of Tyrosine Hydroxylase in Peripheral and Central Adrenergic Neurones by Cold-exposure of Rats
复制标题
冷暴露对大鼠周围和中枢肾上腺素能神经元酪氨酸羟化酶的诱导
作者：
H. Thoenen
由于直接神经刺激或交感神经活动反射增加，肾上腺素能递质去甲肾上腺素的利用增加，导致儿茶酚胺合成立即增加1 -4。有人建议，这种快速适应是一个结果，减少终产物抑制酪氨酸羟化酶的去甲肾上腺素5或增加可用性的辅因子或底物在酶位点4。在这些实验条件下未检测到体外酪氨酸羟化酶活性的变化4，6。然而，最近的研究表明，药物诱导的交感肾上腺活性的增加不仅引起对活性增加的立即、快速调整，而且引起长期适应，这涉及酪氨酸羟化酶7 -9的诱导，酪氨酸羟化酶是儿茶酚胺合成中的限速酶10。研究发现，大鼠冷暴露可增加尿中儿茶酚胺及其代谢物的排泄11，12，并增强外周器官13和中枢神经系统特定区域14中去甲肾上腺素的合成。这项研究表明，长期暴露于寒冷的大鼠引起的体外酪氨酸羟化酶活性的增加，不仅在外周交感神经节和肾上腺髓质，但也在中枢神经系统的部分。
INCREASED utilization of the adrenergic transmitter noradrenaline, resulting from direct nerve stimulation or reflex increase in sympathetic nerve activity, elicits an immediate rise in the synthesis of catecholamines1–4. It has been suggested that this rapid adaptation is a consequence of decreased end-product inhibition of tyrosine hydroxylase by noradrenaline5 or of an increased availability of cofactor or substrate at the enzyme site4. No changes in the in vitro tyrosine hydroxylase activity have been detected in these experimental conditions4,6. It has recently been shown, however, that a drug-induced increase in sympathoadrenal activity provokes not only this immediate, rapid adjustment to the increased activity, but also a long-term adaptation which involves the induction of tyrosine hydroxlyase7–9, the rate-limiting enzyme in the synthesis of catecholamines10. Cold-exposure of rats has been found to increase the excretion of catecholamines and their metabolites in urine11,12 and to enhance the synthesis of noradrenaline in peripheral organs13 and specific regions of the central nervous system14. This study shows that prolonged exposure of rats to cold provokes an increase in the in vitro tyrosine hydroxylase activity not only in peripheral sympathetic ganglia and adrenal medulla, but also in parts of the central nervous system.