This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via Google Scholar Google Scholar Articles by HAEBERLI, A. Articles by WOLLMAN, S. H. Search for Related Content PubMed PubMed Citation Articles by HAEBERLI, A. Articles by WOLLMAN, S. H.

Accumulation and Localization of Radiocalcium in the Rat Thyroid Gland^*

Laboratory of Physiology (A.H., S.H.W.) and the Laboratory of Theoretical Biology (F.K.M.), National Cancer Institute, National Institutes of Health Bethesda, Maryland 20014

Abstract

To determine the rate of accumulation of radiocalcium (⁴⁵Ca) in the thyroid gland, the concentration of radiocalcium was measured in the blood serum and thyroid gland at various time intervals up to 7 days after a single ip injection of ⁴⁵Ca in rats. The ratio of the ⁴⁵Ca concentration in thyroid gland to serum (T:S) increased with the time interval after injection. Thyroid activity was varied by hypophysectomy or by feeding a low iodine diet with or without added thiouracil. The more active the gland, the faster it equilibrated with the serum ⁴⁵Ca and the less was the T:S in the steady state. The equilibration was much slower than for radioiodide, taking several days in normal control rats and hours in vory active glands. Autoradiographs showed that the ⁴⁵Ca concentration was higher in association with the follicular epithelium than with the follicular lumen at 1 h or less after injection. However, at 24 h, the concentration of ⁴⁵Ca was higher in the lumen than elsewhere in the gland. To determine rate constants describing the equilibration, the data in the normal gland were fitted with a model that took account of the differing rates of equilibration in cell and lumen.

The presence of calcium in the lumen indicates that each time the follicular epithelial cell endocytosed stored luminal colloid before secretion, it also took in an appreciable amount of calcium. (Endocrinology 102: 1511, 1978)

Footnotes

^* Permanent address: Medizinische Klinik, Inselspital, CH-3010 Berne, Switzerland.

Received March 21, 1977.