Vascularization and iodide transport down regulation in rat goitre.

This study was designed to investigate, in the rat, the regulation of the amount of thyroid iodide and of its organification during the involution of an experimentally induced goitre. The goitre was obtained by drastic iodine deficiency; male Wistar rats received an iodide deficient diet for 6 months, supplemented with PTU during the last 2 months. The study was followed for 16 days after the beginning of iodide refeeding (daily iodine intake = 50 micrograms). The thyroid iodide, total thyroid organic iodine and plasma iodide, PBI and TSH concentrations were determined from day 0 to 16 and compared to their control values (rats on a normal iodide diet for 6 months). In addition, a stereological study was carried out to determine if the extent of the gland vasculature might be implicated in the regulation of the thyroid iodide content. The plasma TSH concentration was very high and constant for 8 days (2.40 +/- 0.37 and 2.45 +/- 0.43 on day 0 and 8 respectively vs 0.25 +/- 0.12 microgram/ml in control rats), whereas iodination and secretion were blocked for 4 days (0.34 +/- 0.19 and 0.5 +/- 0.1 on day 0 and 4 respectively vs 14.4 +/- 2.0 micrograms 127I/gland in control rats) (Wolff-Chaikoff effect). Thyroid iodide amount increased enormously for 2 days (2.5 +/- 0.6 and 2.45 +/- 0.55 respectively on day 1 and 2 vs 0.09 +/- 0.01 micrograms 127I/gland on day 0), then strongly decreased between 2 and 4 days (1.15 +/- 0.27 127I/gland).(ABSTRACT TRUNCATED AT 250 WORDS)