Gwynne J T, Hess B
Metabolism. 1978 Nov;27(11):1593-600. doi: 10.1016/0026-0495(78)90281-0.
In order to learn more about the mechanism by which high density lipoprotein (HDL) cholesterol is taken up by the adrenal cortex, binding and degradation of human 125I-HDL by suspensions of intact rat adrenal cortical cells have been examined. Cellular accumulation of 125I-HDL was found to occur in two phases. Our results indicate that the initial phase of association results from reversible binding of 125I-HDL to a specific saturable set of membrane binding sites. Binding site affinity appears equal for both rat and human HDL while affinity for human LDL is approximately one order of magnitude less on the basis of apoprotein weight. In addition, isolated rat adrenal cortical cells were found to degrade human 125I-HDL at a rapid rate. Degradation, like binding, can be prevented by addition of excess unlabeled HDL suggesting that binding and degradation are linked. Thus, one mechanism that could account for adrenal uptake of HDL cholesterol is endocytosis, initiated by lipoprotein binding to the HDL specific membrane binding site.
为了更多地了解肾上腺皮质摄取高密度脂蛋白（HDL）胆固醇的机制，研究了完整大鼠肾上腺皮质细胞悬液对人¹²⁵I-HDL的结合和降解情况。发现¹²⁵I-HDL在细胞内的积累分两个阶段进行。我们的结果表明，初始结合阶段是由于¹²⁵I-HDL与一组特定的可饱和膜结合位点可逆结合所致。大鼠和人HDL的结合位点亲和力似乎相等，而基于载脂蛋白重量，对人低密度脂蛋白（LDL）的亲和力约低一个数量级。此外，发现分离的大鼠肾上腺皮质细胞能快速降解人¹²⁵I-HDL。与结合一样，加入过量未标记的HDL可阻止降解，这表明结合和降解是相关联的。因此，肾上腺摄取HDL胆固醇的一种可能机制是内吞作用，由脂蛋白与HDL特异性膜结合位点结合引发。
