A comparison of the influence of 2,4-dinitrophenol on the oxygen consumption of rat brain slices and homogenates.

It is well established that the oxygen consumption of various types of intact cells is augmented when low concentrations of 2,4-dinitrophenol (DNP) or certain ot!her substituted phenols are added to the medium in which the cells are suspended. Slightly higher concentrations depress oxygen consumption. This has been shown for yeast (l-6), luminous bacteria (7), various marine eggs (S-14), orthopteran embryos (15), mammalian sperm (16-19), and several amphibian (20) and mammalian (21-25) tissues. Similar observations have been reported in some studies on glycolysis (cf. (26)). The augmentation phase of the concentration-action curves (cf. (27)) which depict the effect of graded concentrations of DNP (and certain other substituted phenols) on oxygen consumption appears to depend upon factors associated with cell structure or rendered inactive by dilution (cf. (28)), because it has not been observed in cytolyzed material (29) or in cell-free preparations of various enzymes directly concerned in cell respiration (13, 30-32). Recently Reiner (33) has described a rat brain homogenate, reinforced with the known co-factors of glycolysis and with nicotinamide, cyt,ochrome c, and fumamte, which is capable of oxidizing glucose. Moreover Reiner has defined the conditions for maximum activity in this system. In order t,o obt,ain further information regarding the action of the substituted phenols in augmenting cell respirat.ion, which is still imperfectly understood (26, 34, 35), we have compared the influence of graded concentrations of DNP on the oxygen consumption of rat brain slices and homogenates with glucose as the fuel in each case. The results are presented in this paper.