Growth and metabolism of strain L fibroblasts with reference to the actions of uncouplers of oxidative phosphorylation

Abstract

This study is an investigation into some aspects of mammalian cell growth and metabolism in vitro, with particular reference to the actions of uncouplers of oxidative phosphorylation. Oxidative phosphorylation is the mechanism by which the cell utilises the energy made available in biological oxidations, oxidative reactions being linked, or capable of being linked to the phosphorylation of adenosine diphosphate (ADP) by inorganic phosphate (Pi) according to the formal equation

AH₂ + B + ADP + Pi ⇌ A + BH₂ + ATP + H₂O

which is the sum of two reactions which are essentially irreversible

AH₂ + B → A + BH₂ (1)

ADP + Pi → ATP + H₂0 (2)

The oxidative reaction (1) must deliver sufficient energy to drive reaction (2) to the right. Despite its fundamental importance, the me chanism of oxidative phosphorylation has not yet been described. Since the finding of Loomis and Lipmann (1948) that 2 :4- Dinitrophenol (2t4 -DNP) uncouples oxidation from respiratory chain phosphorylations, research into the actions of uncouplers has centred primarily on three types of biological systems - isolated mitochondria and sub units. tissue slices, and micro- organisms. To a lesser extent, ascites tumour cells and red blood cells have been used. With the exception of the work to be described, no investigation of any length appears to have been carried out on tissue culture cells. Of these approaches, the most important information on the mechanism of oxidative phosphorylation and its uncoupling has been derived from investigations of isolated mitochondria and sub units. As a very large number of reviews provide extensive coverage of both historical and recent developments (Lardy and Eivehjam, 1945; Lehninger, 1951, 1955; Chance and Williams, 1956; Slater, 1955, 1958, 1961, 1964; Lehninger and Wadkins, 1962), it is proposed to outline only the more important aspects here as an essential background to the work to be described.