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Vitamin C Depletion and in vitro Uptake and Organification of ¹³¹I by Guinea Pig Thyroid Tissue¹

Department of Human Nutrition and Food, College of Human Ecology, Cornell University, Ithaca, New York 14850

The in vitro uptake and organification of ¹³¹I were investigated in thyroid slices of young female guinea pigs depleted of ascorbic acid for 9, 11, and 15 days, and of pair-fed controls. Thyroids, adrenals, pituitaries, and brain tissues of control and 11- and 15-day-deficient animals were assayed for ascorbic acid. Of all control tissues, the thyroid had the lowest concentration of total ascorbic acid (9.0 mg/100 g tissue). At either 11 or 15 days, the thyroid showed identical and acute depletion of reduced ascorbic acid (0.3 mg/100 g tissue) whereas oxidized levels were comparable to the control (2.0 mg/100 g tissue). At day 11, reduced ascorbic acid levels in other depleted tissues ranged from 10.1 to 11.9 mg/100 g tissue; at day 15, only the adrenal showed further depletion, though less acute than the thyroid. Prior to inanition and weight loss, inorganic ¹³¹I increased (day 9, P < 0.001) with no change in organification; then organic ¹³¹I decreased (day 11, P < 0.002) with no change in uptake. At day 15, both inorganic and organic ¹³¹I declined (P < 0.001 and P < 0.025) concurrent with inanition and weight loss. In all deficient thyroids progressive and statistically significant changes also occurred in intrathyroidal iodinated compounds.

KEY WORDS: • vitamin C • iodide • thyroid • guinea pig

¹ Supported in part by Public Health Service Grant no. AM 08249 from the National Institutes of Health, and by the Nutrition Foundation. The grants are gratefully acknowledged.

² Present address: Department of Food and Nutrition, Texas Tech University, Lubbock, Texas 79409. This paper is part of a thesis presented to the Graduate School of Cornell Univesirty in partial fulfillment of the requirements for the Ph.D. degree. A resume of part of this study was presented at the Annual Meeting of the Federation of American Societies for Experimental Biology in Chicago, April 1971 (Federation Proc. 30: 522 (1971) (abstr.).

Manuscript received 8 November 1971.