Matsuura T, Nagamori S, Hasumura S, Sujino H, Niiya M, Shimizu K
Department of Internal Medicine I, Jikei University School of Medicine, Tokyo, Japan.
Exp Cell Res. 1993 Nov;209(1):33-7. doi: 10.1006/excr.1993.1281.
Stellate cells (SC) in the liver store the most retinoid in the body, but the mechanisms of specific retinoid transport into SC remain to be elucidated. In this study, to analyze the retinoid content of cultured SC, we employed an anchored cell analysis and sorting system (ACAS), which provides fluorescence analysis of single cultured cells under the phase-contrast microscope by utilizing a laser. First, we examined the effect of retinol binding protein (RBP) on retinol transport into cultured SC of rat liver. Rat holo-RBP added to the medium inhibited retinol uptake into SC. We also prepared RBP-free human serum by affinity chromatography using conjugated anti-human RBP IgG and compared retinoid fluorescence of SC cultured in human serum with or without RBP. No significant difference in retinoid fluorescence intensity was observed between SC cultured with and without holo-RBP. Second, the removal of cellular retinol by esterification may be important for the continued uptake of retinol. Retinyl esters are stored in lipid droplets of SC. Therefore we examined the relationship between the lipid droplet number and the retinoid fluorescence intensity in SC which were cultured in medium containing retinol for 1-3 days. The increases in lipid droplet number and in retinoid fluorescence in SC were almost parallel. Progesterone, previously shown to increase the esterification of retinol by lecithin:retinol acyltransferase (LRAT) in vitro, was added to the SC medium; progesterone facilitated retinol uptake in cultured SC. In conclusion, RBP did not facilitate specific retinol transport into SC. However, the specific transport of retinol is likely to be dependent on the intracellular esterification of retinol by LRAT in SC.
肝脏中的星状细胞（SC）储存了体内大部分的视黄醇，但视黄醇特异性转运至星状细胞的机制仍有待阐明。在本研究中，为了分析培养的星状细胞中的视黄醇含量，我们采用了锚定细胞分析和分选系统（ACAS），该系统利用激光在相差显微镜下对单个培养细胞进行荧光分析。首先，我们研究了视黄醇结合蛋白（RBP）对视黄醇转运至大鼠肝脏培养星状细胞的影响。添加到培养基中的大鼠全RBP抑制了视黄醇摄入星状细胞。我们还通过使用偶联的抗人RBP IgG进行亲和层析制备了无RBP的人血清，并比较了在有或无RBP的人血清中培养的星状细胞的视黄醇荧光。在有和无全RBP培养的星状细胞之间，视黄醇荧光强度未观察到显著差异。其次，通过酯化去除细胞内视黄醇可能对视黄醇的持续摄取很重要。视黄酯储存在星状细胞的脂滴中。因此，我们研究了在含有视黄醇的培养基中培养1 - 3天的星状细胞中脂滴数量与视黄醇荧光强度之间的关系。星状细胞中脂滴数量和视黄醇荧光的增加几乎是平行的。先前已证明孕酮在体外可通过卵磷脂：视黄醇酰基转移酶（LRAT）增加视黄醇的酯化，将其添加到星状细胞培养基中；孕酮促进了视黄醇在培养的星状细胞中的摄取。总之，RBP并未促进视黄醇特异性转运至星状细胞。然而，视黄醇的特异性转运可能依赖于星状细胞中LRAT对视黄醇的细胞内酯化作用。
