Transport and metabolism of palmitate in the rat liver. Net flux and unidirectional fluxes across the cell membrane.
The unidirectional fluxes of palmitate across the liver cell membrane and metabolic uptake rates were measured employing the multiple-indicator dilution technique. The following results were obtained: (1) Influx and net uptake rates do not vary proportionally to each other when albumin and palmitate concentrations are varied. (2) Efflux is significant for albumin concentrations in the range between 1.5 and 500 microM. (3) At 150 microM albumin net uptake rates are proportional to the total (bound plus free) extracellular palmitate concentration in the range from 10 to 600 microM; the dependence of influx rates on the palmitate concentration is rather concave up. (4) When albumin and palmitate are both varied at an equimolar ratio, pseudo-saturation appears in the net uptake rates; the influx rates also show pseudo-saturation, but with a declining tendency at the higher concentrations. (5) The intracellular palmitate concentration is strongly influenced by albumin. At very low concentrations of the protein (1.5 microM) the intracellular concentration is practically equal to the extracellular one; at physiological albumin concentrations, however, the intracellular palmitate concentration is less than 2% of the extracellular one. (6) Saturation of net uptake with respect to the intracellular palmitate concentration was not observed with concentrations up to 46 microM.
Ferraresi-Filho
O
O
Laboratory of Liver Metabolism, University of Maringá, Brazil.
Ferraresi
M L
ML
Constantin
J
J
Ishii-Iwamoto
E L
EL
Schwab
A J
AJ
Bracht
A
A
D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D007201:Indicator Dilution Techniques; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D010168:Palmitates / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D010168:Palmitates