Demonstration in vitro of the specific affinity of thyroid cells for iodin

Abstract

It is a well-known fact that thyroid tissue in vivo has a specific affinity for iodin. This has been demonstrated in several ways. The simplest and most obvious means is afforded by taking advantage of the spontaneous active hyperplasia of dogs. Having shown that the per cent. of iodin in the gland varies inversely with the degree of active hyperplasia, we were able to demonstrate that the ability of the gland to take up iodin varies with the degree of active hyperplasia present; or if expressed from the viewpoint of chemistry, the ability of thyroid tissue in vivo to take up iodin varies inversely with the degree of saturation of the gland with iodin. Such relatively large proportions of a given intake of iodin may be stored by the thyroid (for example, the recovery of 4.5 mgm. I from a 7.2 gram thyroid lobe in a dog weighing 8 kilos from a total of 50 mgm. KI given by mouth in 10 days) in vivo that it seems likely the surviving thyroid cells in vitro would exhibit this same affinity, and if so it could readily be demonstrated by perfusion.

We have perfused a large series of spleens, kidneys and thyroids of dogs, using defibrinated blood containing 1/3 (by volume) of Ringer's solution. Iodin as KI was added to the perfusion fluid in amounts varying from 5 mgm. to 40 mgm. All perfusions were carried out at temperatures varying between 35° and 37° C. All the thyroid lobes used were goitrous, varying histologically from marked active hyperplasias to colloid goitres, and in weight from 11 to 81 grams. The perfusions were continued from I to 2 hours, and the glands washed with Ringer's for 20 minutes.