Steeves R M, Lawson D E
Biochim Biophys Acta. 1985 Sep 6;841(3):292-8. doi: 10.1016/0304-4165(85)90071-6.
The effect of 1,25-dihydroxyvitamin D on the activity of S-adenosylmethionine decarboxylase in the duodenal mucosa of vitamin D-deficient chicks was investigated. Enzyme activity increased dose-dependently in a biphasic manner with maximal responses at 1 and 6 h, due to an increase in Vmax in both cases. A second dose of 1,25-dihydroxyvitamin D, administered 6 h after the first, resulted in a significant increase in activity 1 h later, confirming the rapidity of the response. This early response was not seen with ornithine decarboxylase. The increase in S-adenosylmethionine decarboxylase activity particularly at 6 h may be due to a rise in cytosolic calcium, since hydrocortisone, an inhibitor of 1,25-dihydroxyvitamin D-stimulated calcium absorption, attenuates this enzyme's activity. Inhibitors of polyamine biosynthesis such as DL-alpha-difluoromethyl ornithine and methylglyoxal bis(guanylhydrazone) had no effect on calcium absorption, but the significance of this in evaluating the importance of 1,25-dihydroxyvitamin D stimulation of S-adenosylmethionine decarboxylase activity needs further investigation.
研究了1,25 - 二羟基维生素D对维生素D缺乏雏鸡十二指肠黏膜中S - 腺苷甲硫氨酸脱羧酶活性的影响。酶活性呈双相剂量依赖性增加，在1小时和6小时出现最大反应，这两种情况下均因Vmax增加所致。在首次给药6小时后给予第二剂1,25 - 二羟基维生素D，1小时后活性显著增加，证实了反应的快速性。鸟氨酸脱羧酶未出现这种早期反应。S - 腺苷甲硫氨酸脱羧酶活性增加，尤其是在6小时时，可能是由于胞质钙升高，因为氢化可的松是1,25 - 二羟基维生素D刺激的钙吸收的抑制剂，可减弱该酶的活性。多胺生物合成抑制剂如DL-α-二氟甲基鸟氨酸和甲基乙二醛双（脒基腙）对钙吸收没有影响，但这在评估1,25 - 二羟基维生素D刺激S - 腺苷甲硫氨酸脱羧酶活性的重要性方面的意义需要进一步研究。
