Related Experiment Video
Updated: May 12, 2026

Using Caco-2 Cells to Study Lipid Transport by the Intestine
Published on: August 20, 2015
Uptake of L-carnitine by a human intestinal epithelial cell line, Caco-2
1Department of Pediatrics, University of California College of Medicine, Irvine, USA.
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.
Related Concept Videos
Transcellular Transport of Solutes
Glucose Absorption Into the Small Intestine
Renewal of Intestinal Stem Cells
Carrier-Mediated Transport
Active transport involves two types of membrane-spanning transporters: uptake and efflux. Uptake transporters are expressed in the small...
Methods for Studying Drug Absorption: In vitro
The diffusion cell method uses a two-compartment cell, including a donor compartment with the drug solution, which simulates the environment where the drug is applied, and a receptor compartment with a buffer solution, which simulates the environment...
Absorption of Nutrients
Enterocytes, which are specialized polar epithelial cells, line the mucosa of the small intestinal walls. These cells...

