Mechanisms and kinetics of alpha-linolenic acid uptake in Caco-2 clone TC7.
The uptake kinetics of alpha-linolenic acid (18:3(n - 3)), an essential fatty acid, were investigated in the human intestinal cell line Caco-2. Four clones (PD10, PF11, PD7 and TC7) from the heterogeneous parental Caco-2 cells population were used. After a screening step using isolated cells, the TC7 clone was selected for the study of alpha-linolenic acid uptake. [1-(14)C]linolenic acid dissolved in 10 mM taurocholate was presented to the microvillus plasma membrane (apical side) of TC7 differentiated cells, grown on a semi-permeable polycarbonate membrane. The results show that the initial rate of uptake is not a linear function of the 18:3(n- 3) monomer concentration in the incubation medium. In the monomer concentration range studied (0.2 to 36 microM) apical uptake was saturable and followed Michaelis-Menten kinetics (V(max) = 15.4 +/- 0.6 nmol/mg protein per min, K(m) = 14.3 +/- 1.3 microM). In addition, it was temperature- and energy-dependent but was apparently unaffected by the sodium gradient and intracellular metabolic fate of 18:3(n - 3). Excess of unlabeled saturated or unsaturated long chain fatty acids (C16 to C22) led to a 27-68% reduction of [1-(14)C]linolenic acid uptake. Likewise basolateral uptake was saturable (V(max) = 4.9 +/- 0.7 nmol/mg protein per min, K(m) = 8.7 +/- 2.9 microM). These facts argue in favour of the existence in these human intestinal cells of a carrier-mediated transport system for alpha-linolenic acid and probably other long chain fatty acids as well.
Tranchant
T
T
Laboratoire de Nutrition, Faculté de Médecine, Université de Tours, France.
Besson
P
P
Hoinard
C
C
Delarue
J
J
Antoine
J M
JM
Couet
C
C
Goré
J
J
D000230:Adenocarcinoma / Q000378:metabolism*; D000963:Antimetabolites / Q000494:pharmacology; D018938:Caco-2 Cells; D002250:Carbon Radioisotopes; D002455:Cell Division / Q000502:physiology; D002999:Clone Cells; D003110:Colonic Neoplasms / Q000378:metabolism*; D003847:Deoxyglucose / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005227:Fatty Acids / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D008055:Lipids / Q000096:biosynthesis*; D008985:Monensin / Q000494:pharmacology; D009840:Oligomycins / Q000494:pharmacology; D009994:Osmolar Concentration; D012697:Serine Endopeptidases / Q000378:metabolism; D013379:Substrate Specificity; D013696:Temperature; D013997:Time Factors; D017962:alpha-Linolenic Acid / Q000032:analysis / Q000378:metabolism*
D000963:Antimetabolites; D002250:Carbon Radioisotopes; D004791:Enzyme Inhibitors; D005227:Fatty Acids; D007476:Ionophores; D008055:Lipids; D009840:Oligomycins; D017962:alpha-Linolenic Acid; D008985:Monensin; D003847:Deoxyglucose; D012697:Serine Endopeptidases; D005947:Glucose