Fig. 1.

Uptake of biotin by pancreatic beta-TC-6 cells as a function of substrate concentration. Confluent monolayers were incubated at 37°C in Krebs-Ringer buffer, pH 7.4, in the presence of micromolar (1–50 μM) (A) and nanomolar (5–50 nM) (B) concentrations of biotin. Uptake by the carrier-mediated system was calculated as described in materials and methods. Values are means ± SE of at least 3 separate uptake determinations. When not visible, error bars are smaller than the displayed symbol.