Uptake and metabolism of biotin by human peripheral blood mononuclear cells.
We studied the uptake of biotin into human peripheral blood mononuclear cells (PBMC) using [3H]biotin and studied the catabolism of biotin in PBMC using [14C]biotin. Over 30 min, [3H]biotin uptake was greater at 37 degrees C than at 25 degrees C (KT = 2.6 +/- 0.4 nM, maximal velocity = 2.9 +/- 0.2 fmol . 10(6) cells-1 . 30 min-1). Ouabain reduced [3H]biotin uptake to 65% of control values, suggesting that biotin uptake is Na-K-ATPase dependent. Unlabeled biotin and biotin analogs reduced the uptake of [3H]biotin to 22-70% of control values, suggesting the presence of a competition for a structurally specific biotin transporter. When endocytosis by PBMC was stimulated by various acyl glycerols, [3H]biotin uptake was 40-73% of control values; these data are consistent with the hypothesis that stimulated endocytosis reduces biotin transporter density on the cell surface. During a 168-h incubation, PBMC did not catabolize [14C]biotin.
Zempleni
J
J
Department of Pediatrics (Gastroenterology), University of Arkansas for Medical Sciences and the Arkansas Children's Hospital Research Institute, Little Rock, Arkansas 72202, USA.
Mock
D M
DM
D000643:Ammonium Chloride / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D001710:Biotin / Q000097:blood*; D002250:Carbon Radioisotopes; D003078:Colchicine / Q000494:pharmacology; D004075:Diglycerides / Q000494:pharmacology; D004705:Endocytosis; D005001:Ethionine / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism*; D018021:Lithium Chloride / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D013395:Sucrose / Q000097:blood; D013696:Temperature
D002250:Carbon Radioisotopes; D004075:Diglycerides; D000643:Ammonium Chloride; C044295:1,2-dioctanoylglycerol; D013395:Sucrose; D010042:Ouabain; D001710:Biotin; D018021:Lithium Chloride; D003078:Colchicine; D005001:Ethionine