Hendriks H F, Blaner W S, Wennekers H M, Piantedosi R, Brouwer A, de Leeuw A M, Goodman D S, Knook D L
TNO Institute for Experimental Gerontology, Rijswijk, The Netherlands.
Eur J Biochem. 1988 Jan 15;171(1-2):237-44. doi: 10.1111/j.1432-1033.1988.tb13782.x.
The levels of retinoids, retinol-binding protein, cellular retinol-binding protein, cellular retinoic-acid-binding protein, transthyretin and the activities of retinyl palmitate hydrolase and cholesteryl oleate hydrolase were determined in purified parenchymal, fat-storing, endothelial and Kupffer cell preparations, and in liver homogenates from young adult (6-month-old) and old (36-month-old) rats. Retinoid levels were also determined in the plasma from young and old rats. Retinoid contents were determined by HPLC. The binding proteins and transthyretin were measured by specific radioimmunoassays; retinyl palmitate and cholesterol oleate hydrolases were measured by sensitive microassays. The retinoid content of both the liver homogenates and of the fat-storing, and parenchymal cell preparations increased between 6 months and 36 months of age. The cellular distribution of retinoids was similar for the two age groups analyzed with the fat-storing cells being the main retinoid storage sites in the rat liver. Concentrations of retinol-binding protein and transthyretin were high in parenchymal cell preparations. Cellular retinol-binding protein was enriched both in parenchymal and in fat-storing cell preparations; the highest concentrations of cellular retinoic-acid-binding protein were present in fat-storing cell preparations. No major differences were observed between the two age groups in the cellular concentrations and distributions of any of these binding proteins. High activity of cholesterol oleate hydrolase was measured in parenchymal and in Kupffer cell preparations; endothelial cell preparations also contained considerable activities. The distribution of this activity over the various cell types reflects their role in lipoprotein metabolism. Retinyl palmitate hydrolase activity was specifically enriched in parenchymal and in fat-storing cell preparations, consistent with the roles of these cells in retinoid metabolism. No major differences were observed between the two age groups in the cellular distributions of the two hydrolase activities. This study indicates that no major changes occur in the retinoid-related parameters analyzed with age, suggesting that rat liver retinoid metabolism does not change dramatically with age and that retinoid homeostasis is maintained.
在纯化的实质细胞、贮脂细胞、内皮细胞和库普弗细胞制剂以及年轻成年（6个月大）和老年（36个月大）大鼠的肝脏匀浆中，测定了类视黄醇、视黄醇结合蛋白、细胞视黄醇结合蛋白、细胞视黄酸结合蛋白、甲状腺素转运蛋白的水平以及棕榈酸视黄酯水解酶和油酸胆固醇酯水解酶的活性。还测定了年轻和老年大鼠血浆中的类视黄醇水平。类视黄醇含量通过高效液相色谱法测定。结合蛋白和甲状腺素转运蛋白通过特异性放射免疫测定法测量；棕榈酸视黄酯和油酸胆固醇酯水解酶通过灵敏的微量测定法测量。肝脏匀浆以及贮脂细胞和实质细胞制剂中的类视黄醇含量在6个月至36个月龄之间增加。在所分析的两个年龄组中，类视黄醇的细胞分布相似，贮脂细胞是大鼠肝脏中主要的类视黄醇储存部位。视黄醇结合蛋白和甲状腺素转运蛋白的浓度在实质细胞制剂中较高。细胞视黄醇结合蛋白在实质细胞和贮脂细胞制剂中均有富集；细胞视黄酸结合蛋白的最高浓度存在于贮脂细胞制剂中。在这两个年龄组之间，这些结合蛋白的细胞浓度和分布未观察到主要差异。在实质细胞和库普弗细胞制剂中测得油酸胆固醇酯水解酶的活性较高；内皮细胞制剂中也含有相当的活性。这种活性在各种细胞类型中的分布反映了它们在脂蛋白代谢中的作用。棕榈酸视黄酯水解酶活性在实质细胞和贮脂细胞制剂中特异性富集，这与这些细胞在类视黄醇代谢中的作用一致。在两个年龄组之间，两种水解酶活性的细胞分布未观察到主要差异。这项研究表明，随着年龄增长，所分析的类视黄醇相关参数没有发生重大变化，这表明大鼠肝脏类视黄醇代谢不会随着年龄的增长而发生显著变化，并且类视黄醇稳态得以维持。
