No abstract

Harman & Feigelson (1952) used the phase-contrast microscope to assess the morphological changes of isolated heart-muscle mitochondria, and concluded that oxidative phosphorylation is the essential mechanism for maintenance ofmitochondrial form. They also found that uncoupling agents, such as 2:4-dinitrophenol, Janus green and usnic acid, produce swelling of isolated mitochondria. It has also been found that added adenosine triphosphate (ATP) inhibits the swelling of mitochondria (Raaflaub, 1952, 1953 a, b) and that the 'spontaneous' swelling ofmitochondria left at room temperature is paralleled by a fall in the concentration of the intramitochondrial ATP (Brenner-Holzach & Raaflaub, 1954). The reciprocal relationship between water content (or swelling) and oxidative phosphorylation (or availability of 'high-energy' phosphate bonds) in mitochondria has been much emphasized, and this paper records the results ofan investigation into the conditions which prevent the swelling of mitochondria. Part of this work has been communicated to the Biochemical Society (Fonnesu & Davies, 1955). EXPERIMENTAL Abbreviation8. These are as follows: adenosine monophosphate, AMP; adenosine diphosphate, ADP; adenosine triphosphate, ATP; 2:4-dinitrophenol, DNP; inosine monophosphate, IMP; inosine diphosphate, IDP; inosine triphosphate, ITP. Preparation of mitochondria. The method used was very similar to that of Macfarlane & Spencer (1953). All operations were carried out in a cold room at 1°with previously chilled materials. Male albino rats were fasted for 12 hr., stunned by a blow on the head and decapitated. The liver was quickly excised and cooled for 3 min. in partially frozen 0-25M sucrose. The chilled tissue was blotted, passed through a Fischer mincer