Winton Tong

Iodine metabolism of dispersed thyroid cells obtained by trypsinization of sheep thyroid glands

Follicular cells of sheep thyroid glands were dispersed and isolated by a continuous-flow tissue trypsinization procedure. When incubated with [131I]iodine, the isolated cells were shown to retain the capacity for concentrating iodide ion, and for incorporating iodine into iodotyrosines and iodothyronines. They also deiodinated 3,5-diiodotyrosine more actively and 3-iodotyrosine less actively than did thyroid slices. These findings are interpreted as showing that the presence of colloid and follicular structure is not essential for iodide-concentrating function and hormone synthesis by the thyroid gland.

Identification of labeled thyroxine and triiodothyronine in amphioxus treated with 131I

Specimens of the protochordate, amphioxus, were maintained in sea water containing 131I for periods rainging from I h to II days. The utilization of the 131I was studied with the aid of paper-chromatographic techniques. The highest concentration of 131I was found in the endostylar region of these animals, but 131I protein was also found in the notochord, the hepatic cecum, and carcass tissues. 131Ithyroxine and [131I]triiodothyronine were found in this thyroidless organism and clearly identified by co-chromatography with authentic compounds. In contrast to observations made in mammalian thyroid glands, [131I]triiodothyronine was formed in proportions equal to ar greater than those of [131I]thyroxine.

131I utilization by the aquarium snail and the cockroach

Abstract 1. 1. Snails and cockroaches were examined by paper chromatography after 2 to 7 days of treatment with 131 I. In both organisms a labeled product was observed which had a mobility similar to that of thyroxine when chromatographed in a collidine-NH 4 OH solvent mixture, but did not coincide with thyroxine nor with any of 7 other thyroid hormone derivatives when chromatographed with two other solvent systems. Our findings do not support the view that thyroid hormone synthesis can occur in these invertebrates. 2. 2. It is suggested that the formation of organic 131 I in these and other invertebrates is due to the oxidizing action of quinones present as part of a mechanism for the hardening of proteinaceous structural organs .

131I utilization by thyroid tissue of the hagfish

Abstract Iodine utilization by the hagfish, Eptatretus stoutii , was studied at 1, 2, 4, 6 and 10 days after the injection of 131 I. The 131 I was taken up by the thyroid elements dispersed in the gill region and incorporated into protein bound form. Enzymic hydrolysis followed by chromatography of this 131 I protein revealed the presence of [ 131 I]monoiodotyrosine (22–47%), diidotyrosine (13–35%), and very small amounts of thyroxine (0.7–2.2%). [ 131 I]thyroxine was not detectable in plasma of the hagfish until the fourth day after the 131 I injection.

Stimulating effects of cytochrome c and quinones on 131I utilization by cell-free sheep thyroid gland preparations

Abstract 1. 1. The activating actions of FMN, cytochrome c , and certain quinones on the utilization of iodide by cell-free sheep thyroid tissue preparations were studied. 2. 2. 5 · 10 −4 M cytochrome c activated iodide utilization by whole homogenates of thyroid tissue, but not by the isolated particulate fraction. Evidence is presented to show that this activating action of the cytochrome requires a heat-labile component of the soluble fraction. 3. 3. In contrast, FMN stimulated the sheep thyroid particulate fraction but not the whole homegenate. It is concluded that there is a heat-labile substance in the soluble fraction that blocks the action of FMN. 4. 4. Seven napthoquinones and p -benzoquinone were tested. The benzoquinone and 4 of the napthoquinones (including menadione) were effective in stimulating 131 I utilization in both whole homogenates and particulate fractions of sheep thyroid glands. Vitamin K 1 was not effective, while phythiocol and lapachol were strongly inhibitory. 5. 5. FMN, cytochrome c , and the quinones were also tested in a number of control systems containing tyrosine, purified protein, or a number of non-thyroid tissues. 6. 6. It is suggested that iodoprotein formation reported in various 131 I by quinones insects, molluscs, and annelids is the result of the oxidation of the 131 I by quinones present in these organisms as part of a “quinone tanning” mechanism.