Abstract

By the use of homogenates of rat tissues, it was demonstrated that the potential rates of glycolysis of normal tissues are as great or greater than that of tumor tissue. Low rates of glycolysis were obtained by other investigators with slices of normal tissues because of the inability of these tissues, in vitro , to accomplish the initial phosphorylation step in the formation of hexosediphosphate. Evidence has been presented which would indicate that the “hexokinase” reaction is inhibited by some hormone influence, which can be relieved or balanced in vivo but which is nondissociable in vitro . Removal of certain endocrine glands, including the adrenals, pituitary, and gonads, did not relieve this inhibition. Insulin at “near physiological” levels did not relieve the inhibition of hexokinase. Homogenates of Flexner-Jobling rat carcinoma and rat brain are able to glycolyze and esterify phosphate at maximum rates with very low glucose levels (25 mg. per cent) and show slight increases at very high glucose levels (1,440 mg. per cent). In contrast, rat liver, kidney, and diaphragm muscle homogenates appear unable to utilize glucose at low levels and are considerably stimulated at very high glucose levels. High additions of insulin permit the maximum effect at much lower glucose levels. Although insulin effects could be obtained with other rat tissues, none was ever observed in a large number of experiments with homogenates of rat tumor and brain tissues.