Manjunath R, Ramasarma T
Biochem J. 1985 Mar 1;226(2):397-402. doi: 10.1042/bj2260397.
Exposure of rats to heat (39 +/- 1 degree C) stimulated liver tryptophan pyrrolase 2-fold between 3 and 48 h. Plasma corticosterone increased 2-fold after 1 h of heat exposure and decreased to a low value of 50% by 16 h. The effect of heat exposure on the enzyme was obtained in adrenalectomized animals. Stimulation by cortisol and tryptophan of the enzyme was also obtained in heat exposure, and the effects seemed to be additive. The concentration of tryptophan in the liver remained unchanged, and that in the plasma decreased to about 50% at 8 h exposure to heat and reverted to normal by 46 h. Simultaneous administration of noradrenaline to heat-exposed rats had no effect, whereas that of thyroxine partly prevented the stimulation of the enzyme activity. Hypothyroid conditions obtained by thyroidectomy or treatment with propylthiouracil significantly stimulated the enzyme activity. Cycloheximide treatment of heat-exposed rats did not prevent the stimulation of the enzyme activity. The results indicate that the effect of heat exposure on liver tryptophan pyrrolase is obtained, due to the accompanying hypothyroid condition, by increasing the activity of the existing protein by a mechanism possibly different from those known at present.
将大鼠暴露于热环境（39±1℃）中，在3至48小时内肝脏色氨酸吡咯酶活性增加了2倍。热暴露1小时后血浆皮质酮增加了2倍，到16小时时降至低值，仅为初始值的50%。在肾上腺切除的动物中也观察到了热暴露对该酶的影响。在热暴露条件下，皮质醇和色氨酸对该酶也有刺激作用，且二者的作用似乎具有加和性。肝脏中色氨酸的浓度保持不变，而血浆中的色氨酸浓度在热暴露8小时时降至约50%，并在46小时时恢复正常。对热暴露的大鼠同时给予去甲肾上腺素没有效果，而给予甲状腺素则部分地抑制了酶活性的刺激。通过甲状腺切除或用丙硫氧嘧啶治疗导致的甲状腺功能减退状态显著刺激了酶活性。用环己酰亚胺处理热暴露的大鼠并没有阻止酶活性的刺激。结果表明，热暴露对肝脏色氨酸吡咯酶的影响是由于伴随的甲状腺功能减退状态，通过一种可能与目前已知机制不同的机制增加了现有蛋白质的活性而产生的。
