Effect of thiouracil and excess thyroxine on the incorporation of 35S-labelled cysteine in the subcommissural organ of the rat

Abstract

The incorporation of 35S-labelled cysteine in the ependymal cells of the rat's subcommissural organ was studied after thiouracil and excess thyroxine administration. For reference, the incorporation in the ependymal cells of the choroid plexus of the third ventricle was also observed. The incorporation was slightly less 30 minutes after injection of the tracer both in the groups of thiouracil- and thyroxine-treated animals than in the normal rats. At 3 hours, however, the values were above normal level. In the 24-hour groups the rats treated with thiouracil displayed values distinctly elevated from normal level, while those of the rats under thyroxine effect were clearly below it. The ependymas of the subcommissural organ and of the choroid plexus appeared to behave in similar manner in principle. The results is thought to imply retarding effect of thiouracil and accelerating effect of thyroxine on the cysteine metabolism of the ependymal cells and on their potential secretory activity.