Inhibition of Ascorbic Acid Uptake by Endotoxin: Evidence of Mediation by Serum Factor(s)

Abstract

The effect of bacterial endotoxin on the ascorbic acid uptake by 3T6 fibroblasts was studied. Endotoxin inhibited ascorbic acid uptake by fibroblasts in a dose dependent manner. The inhibition by endotoxin takes place only in the presence of unheated serum; decomplementing serum by heat inactivation at 56°C for 30 minutes eliminates endotoxin's inhibitory effect on ascorbic acid uptake. The effect of endotoxin appears to be instantaneous since the inhibition seen in the cells without any preexposure was similar to the cells preexposed to endotoxin for up to 6 hours. Polymyxin B sulfate which is known to bind the lipid A portion of endotoxin did not reverse the inhibition of ascorbic acid uptake caused by endotoxin.