1 Bile salt-enhanced rat jejunal absorption of a macromolecular tracer

Bile salt deconjugation may occur in the jejunun under conditions of fecal colonic overgrowth of the small intestine.We studied the effects of conjugated and deconjugated bile salts on rat jejunal absorption of a macromolecular tracer,horseradish peroxidase(HRP), in an in vivo perfusion system.At a 0.5mM perfusion concentration, only the deconjugated bile salts,cholate and deoxycholate,produced a significant increase in HRP absorption into serum.At this level the bile salts did not produce evidence of morphological damage to villi or absorptive epithelial cell organelles.At a 0.5mm concentration of the conjugated salt,taurocholate,HRP absorption was indistinguishable from that seen in bile salt free preparations.At a higher 5mM concentration,both the conjugated and deconjugated salts increased jejunal HRP absorption into serum over that seen in bile salt free preparations;this absorption was most marked with the deconjugated salts.At a 5mM level,the deconjugated salts also damage cellular organelles,including mitochondria and Golgi apparatus.Our observations suggest that an alteration in the tigh junctional barrier to macromolecular absorption may play a role in some of the enhanced HRP absorption seen in these experiments with low concentrations of DCh.A more extensive cellular damage leading to enhanced HRP transport may occur with higher concentrations of bile salts.