Puyol P, Perez M D, Sanchez L, Ena J M, Calvo M
Facultad de Veterinaria, Universidad de Zaragoza, Spain.
Biochim Biophys Acta. 1995 May 24;1236(1):149-54. doi: 10.1016/0005-2736(95)00041-z.
Caco-2 cell line grown on collagen coated polycarbonate membranes in bicameral chambers has been used to study the effect of the binding of palmitic acid or retinol on the uptake and passage of iodinated beta-lactoglobulin and albumin across cell monolayers. The percentage of beta-lactoglobulin transported through the monolayer was higher than that of albumin, about 50% and 30% of the total protein after 24 h of incubation, respectively. In all cases, less than 1% of protein was retained intracellularly. No differences were found in the uptake and transport of beta-lactoglobulin or albumin in the presence or absence of ligands. Furthermore, uptake and passage across Caco-2 monolayer of retinol or palmitic acid added either bound to beta-lactoglobulin or to albumin have been compared. The percentage of retinol found in the lower chamber was about 35% of the total retinol after 24 h of incubation for both proteins. However, the amount of retinol associated to cells was higher when it was added bound to beta-lactoglobulin than to albumin, about 26% and 10%, respectively. This fact suggests that the metabolic processing of retinol by Caco-2 cells is the rate-limiting step for retinol transport. The percentage of palmitic acid that crossed the monolayer was about 7%, remaining approx. 90% in the cells for beta-lactoglobulin and albumin. These data support the hypothesis that palmitic acid internalized by Caco-2 cells is mainly destined to serve the structural and energy needs. These results show evidence of retinol and palmitic uptake by Caco-2 cells when beta-lactoglobulin or albumin are the donors, and indicate that the type of binding protein does not affect the transport of both ligands through Caco-2 monolayer.
在双室培养箱中，生长于胶原蛋白包被的聚碳酸酯膜上的Caco-2细胞系已被用于研究棕榈酸或视黄醇的结合对碘化β-乳球蛋白和白蛋白跨细胞单层摄取和转运的影响。经单层转运的β-乳球蛋白的百分比高于白蛋白，孵育24小时后，分别约占总蛋白的50%和30%。在所有情况下，细胞内保留的蛋白不到1%。在有或没有配体存在的情况下，β-乳球蛋白或白蛋白的摄取和转运均未发现差异。此外，还比较了与β-乳球蛋白或白蛋白结合添加的视黄醇或棕榈酸跨Caco-2单层的摄取和转运情况。对于两种蛋白质，孵育24小时后在下室中发现的视黄醇百分比约为总视黄醇的35%。然而，当视黄醇与β-乳球蛋白结合添加时，与细胞相关的视黄醇量高于与白蛋白结合添加时，分别约为26%和10%。这一事实表明，Caco-2细胞对视黄醇的代谢加工是视黄醇转运的限速步骤。穿过单层的棕榈酸百分比约为7%，对于β-乳球蛋白和白蛋白，约90%保留在细胞中。这些数据支持以下假设：Caco-2细胞内化的棕榈酸主要用于满足结构和能量需求。这些结果表明，当β-乳球蛋白或白蛋白作为供体时，Caco-2细胞可摄取视黄醇和棕榈酸，并且表明结合蛋白的类型不影响两种配体通过Caco-2单层的转运。
