Effect of energy inhibitors on cell surface diphtheria toxin receptor numbers.

The effects of various metabolic inhibitors on cell-surface receptors for diphtheria toxin were studied. Incubation of Vero cells at 37 degrees C with fluoride, azide, salicylate, and, to a lesser degree, with deoxyglucose resulted in an apparent loss of receptors for the toxin. With some drugs the loss was rapid (half-time approximately 8-9 min) while with others considerably longer time periods were required (half-time greater than or equal to 40 min). The loss of toxin receptors could also be induced by the drugs at 4 degrees C. Washing out the drugs and incubating the cells at 37 degrees C led to a complete restoration of receptors to control numbers. Restoration did not occur if cells were incubated at 4 degrees C. The regain of binding capacity was not dependent on RNA or protein synthesis. It is suggested that metabolic inhibitors may block a continuous process required to maintain toxin receptors in a functional state at the cell surface.