QUANTITATIVEIN VITRORESPONSE OF THYROID TISSUE TO THYROTROPIC HORMONE1

Abstract

In vitro uptake of iodine by beef thyroid minces was measured and found to be proportional to thyrotropic hormone content of the incubation medium. Such a response to TSH was not elicited from thyroid tissue in the form of homogenates. After two hours incubation in 4.0 ml. of Krebs-Ringer-phosphate buffer containing 10 to 20 [mu]c. Nall31, 800 mg. of minced beef thyroid displayed a mean iodine uptake of 22.6% (12.0 to 35.9) in the absence of added thyrotropic hormone. In medium containing 10 m. [mu]/ml. of thyrotropin, mean uptake was 40.2% (22.0 to 69.3). When thyrotropic hormone concentration expressed in logarithms was plotted against % uptake there was a rectilinear response between 1 and approximately 10 m. [mu]/ml. of TSH. The regression coefficient, determined by the responsiveness of the gland, was different for each mince. Analysis of variance of the regression lines indicated a very significant relation between dose and response. In this incubation medium iodine uptake was depressed by 6 x 10-4 [image] Kl. Thyroxine at 4 x 10-5 influenced neither initial iodine uptake nor response to thyrotropic hormone. Uniformity of response of thyroid minces and the magnitude of alterations in iodine uptake induced by TSH suggest the applicability of these techniques for in vitro estimation of thyrotropic hormone.