. Biological structure and function; proceedings. Biochemistry; Cytology. 8 OLOV LINDBERG et al. Inhibition of dinitrophenol- and Mg + ^-activated A TPases by thyroxine and rehited compounds In Fig. I, the effects of thyroxine, triiodothyronine and desamino- thyroxine on the dinitrophenol induced ATPase of rat Hver mitochondria are illustrated. Of the three compounds, desaminothyroxine exhibited the strongest inhibition, giving half-inhibition at a concentration of about 0-02 mM. The effect of the same compounds on the Mg + +-acti- vated ATPase is shown in Fig. 2. For the study of this reactio
. Biological structure and function; proceedings. Biochemistry; Cytology. 8 OLOV LINDBERG et al. Inhibition of dinitrophenol- and Mg + ^-activated A TPases by thyroxine and rehited compounds In Fig. I, the effects of thyroxine, triiodothyronine and desamino- thyroxine on the dinitrophenol induced ATPase of rat Hver mitochondria are illustrated. Of the three compounds, desaminothyroxine exhibited the strongest inhibition, giving half-inhibition at a concentration of about 0-02 mM. The effect of the same compounds on the Mg + +-acti- vated ATPase is shown in Fig. 2. For the study of this reaction a preparation of mitochondrial fragments, obtained after disruption of mitochondria with a rapidly rotating Super-Thurrax blender was mM Fig. I. Effect of L-thyroxine, DL-triiodothyronine and desaminothyroxine on the dinitrophenol-induced ATPase activity of rat liver mitochondria. For experimental details see [76]. The procedure was adapted from Kielley and Kielley [80] who devised it for enriching mitochondrial ATPase free from adenylate kinase. As can be seen in Fig. 2, the ATPase activity of the Kielley and Kielley prepara- tion was also inhibited by the three compounds tested, and again, desami- nothyroxine exhibited the strongest inhibition. The half inhibitory con- centration of desaminothyroxine was roughly the same as in the case of the dinitrophenol-induced ATPase. However, in contrast to this latter reaction, the inhibitions given by the triodothyronine and thyroxine were not progressive with concentration, but levelled off at about 0 • i mM to. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original IUB/IUBS International Symposium (1st : 1960 : Stockholm); International Union of Biochemistry; International Union of Biological Sciences; Goodwin, T. W. (Trevor Walworth); Lindberg, Olov, 1914-. L
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