| Popis: |
A subcellular particulate fraction isolated from baking yeast and having the properties of mitochondria, was found to oxidize succinate simultaneously with the esterification of inorganic phosphate. l -Thyroxine was found to depress the P O ratio significantly. Attempts were made to establish optimum conditions for a demonstration of this action of the hormone. The osmolarity of the pretreatment medium, the concentrations of sucrose, Mg, and albumin, and the pH of the incubation mixture were varied; the effects of these modifications on the uptake of oxygen and inorganic phosphate were determined, as influenced by l -thyroxine. It was observed that conditions producing a maximal rate of phosphorylation were not the most favorable ones for a demonstration of the uncoupling action of the hormone. Under conditions which produced a low rate of phosphorylation, l -thyroxine stimulated the oxidation of succinate markedly. |
