Evidence for Heterogeneous Turnover of Iodine in Rat Thyroid Glands
1966; Oxford University Press; Volume: 79; Issue: 5 Linguagem: Inglês
10.1210/endo-79-5-927
ISSN1945-7170
AutoresLAWSON L. ROSENBERG, G Laroche, JACQUELINE M. EHLERT,
Tópico(s)Thyroid Disorders and Treatments
ResumoThe question of homogeneous vs. heterogeneous turnover of thyroidal iodine was tested in rats by comparing the fractional rates of loss of 127I and of 131I from thyroid glands labeled, each, with a single injection of the radioisotope and then depleted of iodine by chronic administration of propylthiouracil (PTU). Two experiments were done; in Experiment I rats were injected with 131I 4 hr (Group I) or 3 2/3 days (Group II) before initiation of the PTU regimen, and in Experiment II 4 hr (Group I) or 4 days (Group II) before PTU. Specific activities of thyroidal iodine determined at later times from 1 hr to 4 1/4 days (Experiment I) or from 1 hr to 7 3/4 days (Experiment II) decreased logarithmically with time; in each experiment, the slope of the line for Group I was significantly steeper (p < 0.001) than that for Group II, and the slope of each line was significantly different (p < 0.001) from zero. Thus, iodine (131I) which entered the thyroid during a 4-hr period immediately prior to chronic blockage of hormonogenesis with PTU was lost more quickly than “older” iodine accumulated during the period 4 days prior to PTU, and which was, in turn, lost more quickly than 127I that represented a wide spectrum of ages from very old to very new. The data confirm experimental results of Triantaphyllidis (1, 2) and of Schneider (3) and indicate that thyroidal iodine is turned over in a heterogeneous manner. (Endocrinology79: 927, 1966)
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