Oxidative metabolism of funicular tissue. I. Effect of exogenous substrates on oxygen consumption of funicular tissue in vitro]

Umbilical cord slices were incubated with various concentrations of either glucose, pyruvate or succinate. Furthermore the conversion of pyruvate to AcCoA and the oxidation of the latter were assessed respectively by measuring labelled CO2 evolved from 14C-pyruvate labelled on C1 or C2. The results suggest that 1) ADP stores are low since glucose induces a Crabtree effect; 2) the "succinoxidase" complex is far from being saturated and cannot account for the low oxidations observed under basal conditions; and 3) that the limiting step should be looked for either in Krebs' cycle or at the level of Complex I of the electron transport chain.