Stimulationof Glycolysisby PlacentalPolypeptidesand Inhibitionby Duramycin1

Placental polypeptides present in crude preparations of trans forming growth factors stimulate glycolysis when added to quies cent 3T3 cells, normal rat kidney, and chick embryo fibroblasts. The stimulation was apparent over a time period of at least 90 min and was seen at glucose concentrations ranging from 1 to 30 mM. Duramycin, an antibiotic isolated from Streptomyces cinnamomeus, inhibits the polypeptide-stimulated and nonstimulated glycolysis of intact cells, since it permeabilizes cells to P¡ and nucleotides. However, duramycin also inhibits the Na*-K+ATPase as well as the ouabain-insensitive Mg2+-ATPase of plasma membranes. Duramycin has no effect on glycolysis cat alyzed by cell-free extracts of Ehrlich ascites tumor cells in the presence of mitochondrial ATPase but partially inhibits glycolysis when ADP and P¡ are generated by ATPases of plasma mem brane preparations.