Biliverdin accumulation in the caudal intestinal segment of juvenile adult lampreys, Petromyzon marinus L.

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Abstract
The possibility of bile pigment excretion by the caudal intestinal region in lampreys was investigated using spectrophotometry, routine electron microscopy, and an exogenous protein tracer. The green pigment present in the caudal intestines of immediately postmetamorphic and juvenile adult lampreys was found to be biliverdin. Cytoplasmic inclusions, which resembled biliary inclusion bodies and which were not formed as a result of exocytosis of materials at the apical surface, were found in the caudal intestine in absorptive, caveolated, and mucous cells concomitant with the appearance of the biliverdin. Evidence therefore indicates that these inclusions probably contain large quantities of the bile pigment biliverdin and other substances with which it may be complexed. It is suggested that the caudal segment of the adult lamprey intestine serves as a site for the elimination of bile pigment in the form of biliverdin. This method of elimination of bile pigment may be an essential function of the intestine owing to the absence of a bile duct in this animal.