Uptake of taurocholic acid and cholic acid in isolated hepatocytes from rainbow trout.
The uptake of the bile acids cholate (CHA) and taurocholate (TCHA) was studied in isolated hepatocytes from rainbow trout (Oncorhynchus mykiss). Both CHA and TCHA were taken up in a concentration- and temperature-dependent manner with optimum temperature at 15 degrees C and a strikingly efficient uptake even at low temperatures (0-5 degrees C). The total uptake was a combination of a saturable [Michaelis-Menten constant (Km) for CHA, 20 microM; Km for TCHA, 19 microM] and a nonsaturable component. The maximal uptake rate of the saturable component was 416 and 805 pmol.mg protein-1.min-1 for CHA and TCHA, respectively. The uptake of both bile acids was shown to be energy dependent, since it was inhibited by the metabolic inhibitors antimycin A, oligomycin and carbonyl cyanide m-chlorophenylhydrazone. The uptake was clearly Na+ independent, since isosmotic replacement of extracellular Na+ by Li+, choline, or K+ did not inhibit the uptake. Furthermore, it seemed to be independent of the presence of extracellular Cl-, since it was not inhibited by replacement of Cl- with sodium gluconate. On the whole, our results show that the hepatocellular uptake of bile acids in rainbow trout is mediated by a Na(+)-independent carrier system, with characteristics resembling the corresponding transport component in mammalian hepatocytes, but with high efficiency even at low temperatures.
Råbergh
C M
CM
Department of Biology, Abo Akademi University, Turku, Finland.
Ziegler
K
K
Isomaa
B
B
Lipsky
M M
MM
Eriksson
J E
JE
D000818:Animals; D001647:Bile Acids and Salts / Q000378:metabolism; D002469:Cell Separation; D002712:Chlorides / Q000378:metabolism; D019826:Cholic Acid; D002793:Cholic Acids / Q000493:pharmacokinetics*; D004734:Energy Metabolism; D005110:Extracellular Space / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D013656:Taurocholic Acid / Q000493:pharmacokinetics*; D013696:Temperature; D013997:Time Factors
D001647:Bile Acids and Salts; D002712:Chlorides; D002793:Cholic Acids; D013656:Taurocholic Acid; D012964:Sodium; D019826:Cholic Acid