Vitamin A-containing lipid droplets in perisinusoidal lipocytes (or fat-storing cells) of rat liver were found to be exocytotically released from the cells in the form of a ‘lipid droplet-protein complex’ following intraportal injection of retinol (17,33, 67 or 100 µg). Intraportal injection of retinol produced varied numbers and sizes of vacuoles with a limiting membrane in perisinusoidal lipocytes. The substance within the vacuoles exhibited a meshwork-like configuration in sections from slices incubated in a medium for revealing acid phosphatase activity or the corresponding control medium, and was immunoreactive to retinol-binding protein and proteinaceous in nature.The occurrence and number of the vacuoles depended on the dosage of injected retinol, being greatest at a dosage of 100 µg of retinol and becoming progressively less at dosages of 67, 33 and 17 µg. The vacuoles appeared to be formed by vacuolization of cisternae of the rough endoplasmic reticulum. Little or no esterase activity was found in lipid droplets in perisinusoidal lipocytes before the intraportal injection of retinol, but after the injection lipid droplets which had fused with the vacuoles became strongly positive for this enzyme activity. This suggests that hydrolysis of retinyl esters may occur in the process of complex formation in perisinusoidal lipocytes.

Keywords:
Perisinusoidal lipocyte, Lipid droplet release, Immunohistochemistry, Enzyme cytochemistry, Rat liver
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© 1989 S. Karger AG, Basel
1989
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