Detail of "66-02-4"

Reference

Effects of fluoride on thyroid hormone biosynthesis

Effects of fluoride on thyroid hormone biosynthesis. Studies in a highly sensitive test system. Siebenhuener, L.; Miloni, E.; Buergi, H. (Endokrinol. Labor, Med. Universitaetsklin., Bern, Switz.). Klin. Wochenschr., 62(18), 859-61 (English) 1984. CODEN: KLWOAZ. ISSN: 0023-2173. DOCUMENT TYPE: Journal CA Section: 1 (Pharmacology) Section cross-reference(s): 2 Rats were given either 60 or 200 mg/mL F- in the drinking water. This raised the serum F- concn. from 0.165 to 0.246 in the 1st and to 0.576 mg/mL in the 2nd instance. Although the higher F- dose was near the toxic range, no antithyroid effect was obsd. Neither organification of I, nor any subsequent step of thyroid hormone biosynthesis (transformation of monoiodotyrosine [70-78-0] to diiodotyrosine [66-02-4] and then to thyroxine [51-48-9]) were effected. F- had no effect on thyroglobulin content of the thyroid gland or on the degree of iodination of thyroglobulin.

Peroxidatic degradation and ether link cleavage of thyroxine in a particulate fraction of human thyroid

Peroxidatic degradation and ether link cleavage of thyroxine in a particulate fraction of human thyroid. Kubota, Ken; Uchimura, Hidemasa; Mitsuhashi, Tomoaki; Chiu, Shoo Cheng; Kuzuya, Nobuaki; Ito, Kunihiko; Nagataki, Shigenobu (Fac. Med., Univ. Tokyo, Tokyo, Japan). Life Sci., 36(11), 1033-9 (English) 1985. CODEN: LIFSAK. ISSN: 0024-3205. DOCUMENT TYPE: Journal CA Section: 2 (Mammalian Hormones) Section cross-reference(s): 13 The degrdn. of thyroxine (T4) [51-48-9] mediated by thyroid peroxidase [9003-99-0] was examd. in man. A particulate fraction (1000-100,000 ′ g) of normal human thyroid tissue was prepd. and used as crude enzyme. [125I]T4 and unlabeled T4 were incubated with the particulate fraction in buffer contg. glucose and glucose oxidase for generation of H2O2. After incubation, iodoamino acids were extd. with EtOH and the products of T4 degrdn. were analyzed by TLC. In this system, T4 was degraded in time-, temp.-, and pH-dependent manners, but not in the absence of the H2O2 -generating system. The rate of degrdn. was related to concn. of the particulate fraction. The reaction was inhibited by methimazole, propylthiouracil, and catalase. When [3',5'-125I]T4 was used as a tracer, major labeled products of T4 degrdn. were inorg. iodide and EtOH-unextd. fraction; no detectable labeled T3 or rT3 was generated. From a kinetic study by adding various doses of unlabeled T4, the apparent Km value for T4 was 30 mM and the Vmax value was 230 pmol/mg protein/min. When [3,5-125I]T4 was incubated with enzyme prepn., 1/3rd of degraded T4 was recovered as diiodotyrosine (DIT) [66-02-4] and half of [125I]DIT was degraded in parallel incubation. No formation of radiolabeled DIT was obsd. on incubation with Na-125I done in tandem. Apparently, thyroid hormones are metabolized by peroxidase in human thyroid by pathways that include cleavage of ether linkage.