Autoradiographie, eine ideale Methode zur Bestimmung des thyreoidalen Jodumsatzes

Abstract

Autoradiography of rat thyroid glands labeled in vivo with ¹²⁵I is an ideal method for the evaluation of thyroidal iodine turnover. Intra- and interfollicular heterogeneity is demonstrated shortly after injection of the tracer. Due to the fact that different follicles equilibrate at different rates, homogeneous distribution of the label is only obtained after feeding the rats for a long period with ¹²⁵I. Omitting the tracer from the diet has resulted in a ¹²⁵l thyroidal release curve which could best be explained with a three compartment model. The radioactivity remaining in the gland after a prolonged wash-out was found predominantly over the follicular cells and in “dense bodies” within the follicular lumen, suggesting that in addition to heterogeneous equilibration of different follicles a slow turnover iodoprotein could be responsible for the sluggish equilibration and release rate.