The Metabolism of Neoplastic Tissues: The Effect of 2:4-Dinitrophenol on the Respiration of Ascites Tumour Cells*,†

ADDITION of glucose to respiring ascites tumour cells is known to inhibit the endogenous oxidation (Kun, Talalay and Williams-Ashman, 1951; Racker 1956). This phenomenon is called the Crabtree effect (Crabtree, 1929). The inhibition of the respiration by glucose may be considered to represent the reverse situation of the inhibition of glycolysis by oxygen (Pasteur effect). Just as much as the inhibition of glycolysis is not caused by the oxygen per se but by the respiratory processes, so it seems that the inhibition of respiration is not due to glucose per se but to the glycolytic reactions. Whether also the same basic regulatory mechanism is involved is another question. After it was found that glycolysis and respiration were both dependent upon Pi and ADP, the former process because of the substrate phosphorylations and the latter because of the phosphorylations in the mitochondrial respiratory chain which appeared to be coupled to the oxidations, the possibility of a competition between the two processes was recognized (Johnson, 1941; Lynen, 1941, 1956, 1958). It is now generally assume

The Metabolism of Neoplastic Tissues: The Effect of 2:4-Dinitrophenol on Glycolysis and ATP-Dephosphorylation of Ascites Tumour Cells and Homogenates*,†

RESPIRATION and glycolysis are both processes which require inorganic phosphate and adenine nucleotides. The inhibition of glycolysis by respiration (Pasteur effect) in both normal and neoplastic tissue, and the reverse situation-the inhibition of respiration by glycolysis ( " reversed Pasteur effect " or Crabtree effect)in neoplastic tissue and especially in ascites tumour cells, may be explained on the basis of a competition between the two processes at the level of the accompanyin

The Metabolism of Neoplastic Tissues: Oxidation of Fatty Acids and Glucose by Ascites Tumour Cells in the Absence and Presence of 2:4-Dinitrophenol*,†

IT is a well-known fact that the endogenous respiration of tumour slices is hardly, if at all, stimulated in the presence of glucose; in many cases even an inhibition of the oxygen consumption has been observed (Crabtree effect; Crabtree, 1929). The latter effect is especially pronounced in ascites tumour cells (Kun, Talalay and Williams-Ashman, 1951; Racker, 1956). Following the early studies of Dickens and Simer (1930) on the respiratory quotients of tumours, it has become increasingly clear in recent years that fatty acid oxidation constitutes an important metabolic pathway in tumours. Thus, slices of solid tumours (Chapman, Brown, Chaikoff, Dauben and Fanash, 1954) and isolated tumour mitochondria (Emmelot and Bos, 1955a, 1955b, 1957; Emmelot, Bos, Brombacher and Hampe, 1959) have been found to oxidize added fatty acids, whereas solid and ascites tumours labelled in vivo with 14C-palmitate, have been reported to liberate 14C-carbon dioxide in appreciable quantity on incubation in vitro (Medes, Paden and Weinhouse, 1957). The respiratory quotients of ascites tumour incubated in the absence of oxidizable substrate is also indicativ

HEXAGONAL ARRAY OF SUBUNITS IN TIGHT JUNCTIONS SEPARATED FROM ISOLATED RAT LIVER PLASMA MEMBRANES

Solubilization of isolated rat liver plasma membranes in 1% deoxycholate and centrifugation yielded a fraction (pellet) that consisted mainly of tight junctions (zonulae occludentes). An hexagonal array of subunits similar to that previously found in a number of the unfractionated plasma membranes was demonstrated in all the membrane sheets of these preparations by negative staining. It is concluded that the hexagonal subunit pattern is present in the tight junctions, and that this structural differentiation may be related to the intercellular diffusion afforded by the junctional membrane

Studies on Isolated Tumour Mitochondria. Phosphate Release from Adenosine Di- and Triphosphates

PREVIOUS work has shown that mitochondria prepared from certain tumour strains in isotonic sucrose containing 0.001 M EDTA, * exhibited higher ATPand DPN-splitting activities than the mitochondria from other tumours (Emmelot, Bos and Brombacher, 1956). When the former were added to fresh liver mitochondria, the octanoate- or BHB-oxidation of the liver mitochondria became completely inhibited in the combined system (Emmelot and Bos, 1955a, 1955b, 1956a). It was found that the DPNase inhibitor NAA, or DPN itself, re-established the oxidation when the D-isomer of BHB served as a substrate in the combined system of liver and tumour mitochondria (Emmelot and Bos, 1955b, 1956a). The oxidation of the L-isomer of BHB, however, still remained blocked under the latter conditions. This difference in behaviour of the liver mitochondria in the presence of the tumour mitochondria in respect to the oxidation of the two isomers was explained on account of the co-factors necessary for oxidation, which have been shown to be dissimilar (Lehninger and Greville, 1953). The latter authors found that the oxidation of D-BHB by rat liver mitochondria proceeded independently of ATP in that the free acid was oxidized, whereas L-BHB needed ATP for the formation of its CoA-derivative, L-BHByl-CoA being the form in which the L-isomer was oxidized. DPN acted as coenzyme of both the D-BHB and the L-BHByl-CoA dehydrogenases. Thus, by adding DPN to the combined system of liver and tumour mitochondria, the oxidation of D-BHB might easily be repaired, but the "ATPase" activities of the tumour mitochondria would render the oxidation of L-BHB impossible by depriving the liver mitochondria of ATP. In the present communication direct evidence is presented for the uncoupling action of certain tumour mitochondria on the phosphorylative processes of the liver mitochondria. Related experiments dealing with the phosphate release from ATP and ADP by these and other tumour mitochondria under various experimental conditions are also described and compared with the results obtained with mouse liver mitochondria

The Metabolism of Neoplastic Tissues: the Inter-relationship between Oxidative and Glycolytic Mechanisms in Ascites Tumour Cells

ONE of the most interesting aspects of the metabolism of ascites tumour cells is their moderately high endogenous respiration which is depressed in the presence of glucose ( " Crabtree effect ") (Kun, Talalay and Williams Ashman, 1951). This phenomenon is the reverse of the classical Pasteur effect. Racker (1956) and Chance and Hess (1956) have argued that the Crabtree effect might be due to a shuttling of adenine nucleotides between the cytoplasm and the mitochondria, while Brin and McKee (1956) have shown that the concentration of inorganic phosphate might condition the inhibition of respiration by glycolysis. The sharing of these compounds between the two processes of carbohydrate breakdown has also been advocated to explain the Pasteur effect (Johnson, 1941; Lynen, 1941, 1956), but convincing evidence is still lacking (Aisenberg, Reinafarje and Potter, 1957). The depression of the oxygen consumption brought about by glacose addition to the ascites cells is accompanied by a shift in the respiratory quilotient from 0.85 (indicative of lipid oxidation) to 1.0 (Seelich, Weigert and Letnansky, 1956