A crabtree effect in amytal- or progesterone-treated ascites tumor cells

The effect of glucose on respiration associated with succinate oxidation was studied with intact ascites tumor cells treated with amytal or progesterone which inhibit the oxidation of reduced diphosphopyridine nucleotide (DPNH). The addition of glucose produced a significant depression in the rate of oxygen consumption associated with succinate oxidation. This inhibitory effect was observed in the presence of uncoupling agents but was partially released by the addition of Tris or phosphate in concentrations with high buffering capacity. Neither glucose in the presence of iodoacetatc nor 2-dcoxyglucose exerted an inhibitory effect on this respiration, a finding which is in contrast to the classic Crabtree effect. Furthermore, in the normal intact cells, glucose partially released the pronounced inhibitory effect of 2-deoxyglucose and vice versa; it is therefore concluded that the inhibitory effect produced by 2-deoxyglucosc differs from that produced by glucose. The data are compatible with the explanation that a factor in this depression of respiration is a change in intramitochondrial pH as a consequence of intracellular acidification.