人肠上皮细胞系Caco-2对左旋肉碱的摄取。

Uptake of L-carnitine by a human intestinal epithelial cell line, Caco-2.

作者信息

McCloud E, Ma T Y, Grant K E, Mathis R K, Said H M

机构信息

Department of Pediatrics, University of California College of Medicine, Irvine, USA.

出版信息

Gastroenterology. 1996 Dec;111(6):1534-40. doi: 10.1016/s0016-5085(96)70015-x.

DOI:10.1016/s0016-5085(96)70015-x

PMID:8942732

Abstract

BACKGROUND & AIMS: The mechanism of intestinal uptake of L-carnitine is controversial. The aim of this study was to clarify the mechanism and regulation of L-carnitine uptake.

METHODS

Uptake of [3H]-L-carnitine was measured across the apical membrane of confluent monolayers of Caco-2 cells.

RESULTS

[3H]-L-carnitine uptake was linear and appreciable for up to 7 minutes with minimal metabolic alteration, was temperature- and Na(+)-(but not pH-) dependent, and included a saturable component with an apparent Michaelis constant of 45.5 +/- 6.5 mumol/L and a maximum velocity of 83.5 +/- 5.6 nmol.mg protein-1.5 min-1. Unlabeled L-carnitine and its structurally related analogues significantly (P < 0.01) inhibited [3H]-L-carnitine uptake, whereas unrelated compounds were ineffective. L-Carnitine uptake was also energy-dependent, being significantly (P < 0.01) inhibited by metabolic inhibitors. Our results also suggested that a calmodulin- but not a protein kinase C- or protein kinase A-mediated pathway plays a role in regulating L-carnitine uptake by Caco-2 cells.

CONCLUSIONS

L-carnitine uptake by intestinal epithelial cells (Caco-2) involves a carrier-mediated system that is temperature-, Na(+)-, and energy-dependent and seems to be under the regulation of a calmodulin-mediated pathway.

摘要

背景与目的

左旋肉碱的肠道吸收机制存在争议。本研究旨在阐明左旋肉碱吸收的机制及调节方式。

方法

通过测量[3H]-左旋肉碱跨Caco-2细胞融合单层顶膜的摄取情况进行研究。

结果

[3H]-左旋肉碱摄取在长达7分钟内呈线性且显著，代谢改变极小，其摄取依赖温度和钠离子（而非pH值），包含一个可饱和成分，表观米氏常数为45.5±6.5μmol/L，最大速度为83.5±5.6nmol·mg蛋白-1·5min-1。未标记的左旋肉碱及其结构相关类似物显著（P<0.01）抑制[3H]-左旋肉碱摄取，而无关化合物则无此作用。左旋肉碱摄取也依赖能量，代谢抑制剂可显著（P<0.01）抑制其摄取。我们的结果还表明，钙调蛋白介导而非蛋白激酶C或蛋白激酶A介导的途径在调节Caco-2细胞左旋肉碱摄取中起作用。