CONTENT OF DOLICHOL AND RETINOL IN ISOLATED RAT NONPARENCHYMAL LIVER-CELLS

The liver sinusoids, that are considered as a functional unit, harbour four types of sinusoidal cells (Ito, Kupffer, endothelial and pit cel ls). Dolichol content has been determined in many tissues and subcellu lar compartments, alteration has been reported in many types of liver injury, but until now no data are available on its content in every ty pe of sinusoidal non-parenchymal liver cells. Dolichol and retinol met abolism might intersect in their traffic in biological membranes. Inte rcellular as well as intracellular exchange of retinoids is an essenti al element of important processes occurring in liver cells. It has bee n suggested that the role of dolichol, besides being a carrier of olig osaccharides in the biosynthesis of N-linked glycoproteins, may be to modify membrane fluidity and permeability, and facilitate fusion of me mbranes. Dolichol in the membrane is intercalated between the two halv es of the phospholipid bilayer, but its exact disposition is not known and the movement and distribution of retinoid in membranes may vary w ith the geometry of the membranes. Therefore the aim of this study is to obtain a global understanding of the sinusoidal system regarding do lichol and retinol content in each type of isolated rat liver sinusoid al cell, in normal conditions and after vitamin A administration. The information that can be drawn from the present results is that with no rmal vitamin A status of the animal, the dolichol content is almost un iform in all liver cells. After vitamin A supplementation, a great inc rease of dolichol, together with the known increase of retinol, can be measured only in a subpopulation of the Ito cells, the Ito-l subfract ion. Therefore in the cells that are present in the hepatic sinusoid, different pools of dolichol may have separate functions. Because retin ol traffic among cells, membranes and plasma still remains to be fully understood, roles of dolichol in the exchange of vitamin A among sinu soidal liver cells are discussed. (C) 1998 John Wiley & Sons, Ltd.