TOTAL PARENTERAL-NUTRITION ASSOCIATED ALTERATIONS IN HEPATOBILIARY FUNCTION AND HISTOLOGY IN RATS - IS LIGHT EXPOSURE A CLUE

Light exposure of amino acids, especially in the presence of photosens itizers such as riboflavin, has been shown to result in photoproducts that are toxic both in vivo and in vitro. Provision of photooxidized s ingle amino acids has been shown to result in hepatic dysfunction in b oth gerbils and rats. However, studies of the effects of light exposur e of complete nutrient mixtures (glucose-amino acid-vitamins) on hepat obiliary responses are limited. These are important because, in clinic al practice, total parenteral nutrition (TPN) solutions are continuall y exposed to light and because hepatic dysfunction is the most common metabolic aberration associated with TPN. Studies were conducted to co mpare the effects of TPN that had been exposed to light (+L) or protec ted from light (-L) on hepatobiliary function of rats. TPN solutions w ere either exposed to light or protected from light for 24 h and then infused into rats for 10 d. Data for enterally fed rats are also shown for comparison with parenterally fed animals. +L animals lost more we ight and had lower bile flow, higher taurocholate output in bile, high er biliary osmolarity, and higher inorganic phosphate in bile. Hepatic histology demonstrated scattered foci of necrosis in eight of the eig ht +L animals and in only one of eight -L animals. These data demonstr ate that protection of TPN solutions from light minimizes TPN-associat ed alterations in hepatobiliary function and histology. These histolog ic changes observed in the +L animals are in contrast to previous repo rts of TPN-induced histologic changes, suggesting a different mechanis m. Our observations suggest that consideration be given to the implica tions of exposing TPN solutions to light.