ABSTRACT
In vitamin A-sufficient rats, most of the chylomicron remnant retinyl esters taken up by hepatocytes is transferred as retinol to perisinusoidal stellate cells in the liver (28). Since stellate cells can take up the REPretinol complex and hepatocytes secrete retinol bound to RBP, it was suggested that RBP mediates the transfer from hepatocytes to stellate cells (29). The transfer of retinol from hepatocytes to stellate cells is too rapid to be accounted for by a secretion of RBP-retinol from hepatocytes to the general circulation followed by retinol being taken up liver stellate cells. During an in situ perfusion of rat livers, we observed that labeled retinol was transferred from hepatocytes to stellate cells. Furthermore, addition of antibodies against RBP blocked the transfer, indicating that RBP was the transport protein mediating the iransfer of retinol from hepatocytes to stellate cells
In mammals, 50--80% of the body's total retinol (retinol plus retinyl esters) is normally present in the liver. Under most conditions, stellate cells contain about 90-95% of the liver total retinoL Ninety-eight percent of the stellate cell vitamin A is in the form of esters together in cytoplasmic lipid droplets. The normal reserve of vitamin A in stellate cells is adequate to last for several months (6-9) (Figure 5).
