Guerrero J M, Puig-Domingo M, Reiter R J
Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284.
Endocrinology. 1988 Jan;122(1):236-41. doi: 10.1210/endo-122-1-236.
Type II T4 5'-deiodinase (5'-D) activity was studied in pineal gland, frontal cortex, and anterior pituitary of male rats. Enzymatic activity was determined by the release of 125I using [3',5'-125I]T4 as substrate. Daytime levels of 5'-D activity were maximal for anterior pituitary (346.2 +/- 142.5 fmol 125I released/mg protein.h), followed by pineal gland (61.5 +/- 8.7 fmol 125I released/mg protein.h) and frontal cortex (3.1 +/- 0.5 fmol 125I released/mg protein.h). Twenty-four-hour fluctuations of 5'-D activity were apparent in the pineal gland and cortex. For pineal, peak 5'-D activity (43.4 +/- 11.4 fmol 125I released/gland.h) occurred at 0100 h, with values at this time being 8-fold greater than basal daytime levels. Superior cervical ganglionectomy (SCGX) or exposure to continuous light (LL) completely abolished the nocturnal rise of 5'-D activity. Treatment with iopanoic acid also inhibited 5'-D activity in pineal (32.1 +/- 3.5 vs. 18.8 +/- 1.7 fmol 125I released/gland.h) without influencing either the N-acetyltransferase activity or the melatonin content. In cortex, peak 5'-D activity occurred at 0500 h (5.3 +/- 0.4 fmol 125I released/mg protein.h), with values at this time being 1.5-fold greater than basal daytime levels. SCGX moderately depressed enzymatic activity, while LL exposure strikingly enhanced the nocturnal increase (11.7 +/- 1.1 vs. 19.3 +/- 2.4 fmol 125I released/mg protein.h at 0300 h). 5'-D activity exhibited no 24-h fluctuation in the anterior pituitary gland, and neither SCGX nor LL exposure affected enzyme levels in this tissue. Our data demonstrate the existence of a 24-h rhythm of type II T4 5'-D activity in pineal gland and cortex, with peak levels occurring at night; in pineal, the sympathetic neural input is indispensable for the rhythm, since SCGX prevented it. In cortex, the apparent paradoxical effect of LL and SCGX on 5'-D activity indicates that other mechanisms are involved in its regulation.
在雄性大鼠的松果体、额叶皮质和垂体前叶中研究了II型T4 5'-脱碘酶（5'-D）的活性。以[3',5'-125I]T4为底物，通过125I的释放来测定酶活性。垂体前叶的5'-D活性白天水平最高（346.2±142.5 fmol 125I释放/毫克蛋白·小时），其次是松果体（61.5±8.7 fmol 125I释放/毫克蛋白·小时）和额叶皮质（3.1±0.5 fmol 125I释放/毫克蛋白·小时）。松果体和皮质中5'-D活性有24小时的波动。对于松果体，5'-D活性峰值（43.4±11.4 fmol 125I释放/腺体·小时）出现在0100时，此时的值比白天基础水平高8倍。颈上神经节切除术（SCGX）或持续光照（LL）完全消除了5'-D活性的夜间升高。用碘番酸处理也抑制了松果体中的5'-D活性（32.1±3.5对18.8±1.7 fmol 125I释放/腺体·小时），而不影响N-乙酰转移酶活性或褪黑素含量。在皮质中，5'-D活性峰值出现在0500时（5.3±0.4 fmol 125I释放/毫克蛋白·小时），此时的值比白天基础水平高1.5倍。SCGX适度降低了酶活性，而LL暴露显著增强了夜间升高（0300时为11.7±1.1对19.3±2.4 fmol 125I释放/毫克蛋白·小时）。垂体前叶中5'-D活性没有24小时波动，SCGX和LL暴露均不影响该组织中的酶水平。我们的数据表明，松果体和皮质中存在II型T4 5'-D活性的24小时节律，峰值水平出现在夜间；在松果体中，交感神经输入对于该节律是不可或缺的，因为SCGX阻止了它。在皮质中，LL和SCGX对5'-D活性的明显矛盾作用表明其调节涉及其他机制。
