Unconjugated bilirubin andthebile fromlight exposed Gunnrats inhibit intestinal waterandelectrolyte absorption

SUMMARYJaundiced babies undergoing phototherapy often develop diarrhoea. Thecauseofitis still uncertain. Increasing evidence supports arole ofasecretory mechanism forthediarrhoea. We therefore studied theeffects ofbile fromcongenitally jaundiced ratsundergoing phototherapy andof unconjugated bilirubin onratsmall intestine invivo andinvitro. Results suggest that: (1)thebile fromhomozygous Gunnratsunderphototherapy hasananti-absorptive effect whentested inthe perfused jejunum ofnormal Wistar rats; (2) unconjugated bilirubin hasadosedependent secretory effect ontheintestinal transport ofwaterandelectrolytes, whentested inthesamesystem. Alteration ofcyclic AMP orcyclic GMP,knownintracellular mediators ofsecretion, wasnotobserved. We conclude that free bilirubin isanintestinal secretagogue acting byanasyetunknownmechanism, that maymediate thesecretory typeofdiarrhoea injaundiced neonates undergoing phototherapy.