[Influence of L-thyroxine upon the ratio between protein-bound SH- and S-S-groups (author's transl)]

In normal rats and in rats with mercury-induced tubular lesions without or with successive L-thyroxine treatment, the number of SH-groups and the total of SH- and S-S-groups in different segments of the nephron were calculated over a period of time by means of a photometric assay. The quantity of SH-groups was increased by low doses of sublimate but reduced by exogenous L-thyroxine, the whole of SH- and S-S-groups summing up to a constant quantity throughout. (Following application of high doses of sublimate, a loss of SH- as well as S-S-groups was observed, due to cellular destruction.) Connection and splitting of S-S-bridges, respectively, corresponded to changes in certain parameters of cell function, for instance resorptive capacity. A hypothesis is proposed stating that a fundamental effect of thyroid hormone is exerted by a biochemical action upon the ration between SH- and S-S-groups, permeability of the cellular and mitochondrial membranes being raised when the numerical proportion of S-S-bonds is high. Stimulation of enzymatic activity and metabolic processes would therefore result adaptively from the augmentation of substrate supply within the cell organells.