Active transport of lead-210 by everted segments of rat duodenum

Everted gut sacs prepared from rat duodenum can transfer 210Pb from mucosal to serosal surfaces against concentration gradients in vitro. The mechanism requires oxygen and is significantly inhibited by sodium azide, sodium iodoacetate, 2,4-dinitrophenol, sodium cyanide, and sodium fluoride. Lack of oxygen or the presence of metabolic inhibitors produced greater relative inhibition of net serosal transfer but greater absolute decrements of net mucosal uptake. Treatment of rats prior to sac preparation with either intravenous FeCl2 or endotoxin, or the addition of FeCl2 to the mucosal medium, selectively inhibited net serosal transfer. Net mucosal uptake and net serosal transfer were significantly negatively correlated with animal weight. Jejunal or ileal sacs did not actively transport 210Pb.