Studies on the Mechanism of Action of the in vitro PGB(x) Effect. I. Composition of Reaction Medium of PGB(x) Effect.

The mechanism of action of PGBx in Rat Liver Mitochondria (RLM) oxidative phosphorylation was studied by determining the necessity of each component of the reaction medium. These components maybe classified as essential, e.g. Pi, Mg(++), phosphate acceptor and oxidizeable substrate, or non-essential, e.g. KCL and BSA. Although the phosphate acceptor was an absolute requirement for the PGBx effect, all adenine nucleotides, singly or in combination, as well as the glucose-ADP-hexokinase system were satisfactory. Of the oxidizeable substrates tested using the experimental conditions described here, only two did not give positive PGBx effects: Beta-hydroxybutyrate and externally reduced NAD. In addition, the PGBx effect can only be demonstrated with isolated mitochondria exposed to hypotonic conditions at 27 C for a time period that will reduce the phosphorylation level to about 5% of that obtained with undegraded mitochondria. (Author)