Cellular localization of liver vitamin A in rats given total parenteral nutrition (TPN) solutions intravenously or orally.

The cellular localization of liver vitamin A was determined in rats, depleted of retinol, whose vitamin A stores were repleted orally or by total parenteral nutrition (TPN) to determine if the route of vitamin administration affected storage location. Solutions containing dispersions of retinyl palmitate were infused into the TPN group and fed orally to controls for 5 days. The site of liver vitamin A storage was determined by correlating vitamin A-specific autofluorescence in frozen sections with the presence of lipid droplets in oil red O preparations, in 1-micron Epon sections and in sections prepared for electron microscopy. Both the vitamin A autofluorescence and oil red O staining were concentrated along the sinusoids in rats both infused with TPN solution and orally fed. Examination of thin sections at higher magnification showed that most of the lipid droplets containing vitamin A were localized near the sinusoidal side of the parenchymal cell cytoplasm, corresponding to the vitamin A autofluorescence and oil red O distribution. There were very few lipid droplets in the stellate cells and none in the Kupffer cells. The results indicate that vitamin A infused in TPN solutions is stored in the same cellular location as orally ingested vitamin A.