Mitogen-induced proliferation increases biotin uptake into human peripheral blood mononuclear cells

We sought to determine whether the proliferation of immune cells affects th e cellular uptake of the vitamin biotin. Peripheral blood mononuclear cells (PBMC) were isolated from healthy adults. The proliferation of PBMC was in duced by either pokeweed lectin, concanavalin A, or phytohemagglutinin. Whe n the medium contained a physiological concentration of [H-3]biotin, nonpro liferating PBMC accumulated 406 +/- 201 amol [H-3]biotin.10(6) cells(-1).30 min(-1). For proliferating PBMC, [H-3]biotin uptake increased to between 3 30 and 722% of nonproliferating values. Maximal transport rates of [H-3]bio tin in proliferating PBMC were also about four times greater than those in nonproliferating PBMC, suggesting that proliferation was associated with an increase in the number of biotin transporters on the PBMC membrane. The bi otin affinities and specificities of the transporter for proliferating and nonproliferating PBMC were similar, providing evidence that the same transp orter mediates biotin uptake in both states. [C-14]urea uptake values for p roliferating and nonproliferating PBMC were similar, suggesting that the in creased [H-3]biotin uptake was not caused by a global upregulation of trans porters during proliferation. We conclude that PBMC proliferation increases the cellular accumulation of biotin.