ABSTRACT
The mechanism of the in vitro PGBx effect on mitochondria was studied by determining the specific requirements of the assay system composition. These studies showed that (a) rat liver mitochondria must first be exposed to hypotonic media containing PGBx under aerobic conditions, (b) oxygen, Pi, Mg++, phosphate acceptor (nucleotides), and some oxidizable substrates are essential components to yield optimal phosphorylation values. KCl and bovine serum albumin are non-essential components. With regard to nucleotide acceptor specificity, the AMP, ADP, and glucose-ADP-hexokinase systems were satisfactory. With regard to substrate specificity, only beta-hydroxybutyrate and externally reduced NAD+ were unsatisfactory. The requirement for oxygen was twofold: (a) as an absolute requirement for oxidative phosphorylation, and (b) as a requirement for the hypotonic degradation of mitochondria. These results suggest that PGBx reacts with mitochondria to "protect" against degradation during aerobic hypotonic exposure.
Subject(s)
Mitochondria, Liver/drug effects , Oxidative Phosphorylation/drug effects , Prostaglandins B/pharmacology , Prostaglandins/pharmacology , Anaerobiosis , Animals , Mitochondrial Swelling/drug effects , Nucleotides/pharmacology , Osmolar Concentration , Polymers , Rats , Serum Albumin, Bovine/pharmacologyABSTRACT
On the basis of the interaction between tritiated PGBx and rat liver mitochondria, it appears that PGBx interacts with rat liver mitochondria to form a complex. At low PGBx-mitochondrial ratios, one effect of this complex formation is to stabilize the phosphorylation activity of rat liver mitochondria when exposed for short times to hypotonic solutions. At higher PGBx-mitochondrial ratios, PGBx fails to show this effect. At low PGBx concentrations, PGBx is also shown to inhibit release of amino acids and proteins as well as glutamic acid dehydrogenase and monoamine oxidase from the mitochondria and to inhibit mitochondrial swelling.
Subject(s)
Mitochondria, Liver/drug effects , Mitochondrial Swelling/drug effects , Prostaglandins B/pharmacology , Prostaglandins/pharmacology , Amino Acids/metabolism , Glutamate Dehydrogenase/metabolism , Mitochondria, Liver/metabolism , Monoamine Oxidase/metabolism , Oxidative Phosphorylation/drug effects , Permeability , Polymers , Prostaglandins B/metabolism , Succinate Dehydrogenase/metabolismABSTRACT
Bovine serum albumin (BSA) interacts with PGBx, a polymeric derivative of 15-keto-prostaglandin B1, to form a complex that does not exhibit the fluorescence of free BSA. The complex is soluble at pH 5.2 in contrast to free PGBx, which is insoluble. Molar ratio of the BSA-PGBx complex is 1:18. This complexing appears to suppress the ability shown by non-complexed PGBx to reactivate phosphorylation in degraded isolated rat liver mitochondria.
