Relative amount and ester composition of vitamin A in rat hepatocytes as a function of the method of cell preparation and of total liver stores.

The aim of this study was to determine the cellular distribution of vitamin A in the liver of adult, well-nourished Sprague-Dawley rats with different stores of this vitamin. Three groups of three rats each were fed AIN-76 diet. Each group received an oral supplement of either 0, 2, or 12 mg of retinol. Retinol and retinyl esters were measured in the whole liver, in hepatocytes isolated either by gravity sedimentation or by centrifugal elutriation, and in the supernatant solution recovered after hepatocyte sedimentation. Dietary supplementation with vitamin A increased the liver stores from 138 to 390 micrograms/g. A mean of 5% of the liver vitamin A was found in hepatocytes isolated by centrifugal elutriation. This percentage tended to decrease as liver vitamin A increased. In contrast, a mean of 38% of total liver vitamin A was found in hepatocytes isolated by gravity sedimentation over a threefold range of liver reserves. Whereas the retinol concentration in hepatocytes remained constant, the percentage of total vitamin A as retinyl esters, which accounted for more than 96% of the total vitamin A, increased as liver stores increased. The retinyl ester composition was similar in all three groups, major esters being palmitate (76-82%), stearate (9-12%), oleate (5-7%), and linoleate (3-4%). Over a threefold range of liver vitamin A concentrations in well-nourished rats, therefore, we estimate that only 10-20% of the total vitamin A in liver is present in the parenchymal cells.