Table 1.

Concentration efficiency of TfR in clathrin-coated pits in HEp-2 cells as determined by immunogold labeling^a

	% of surface area occupied by clathrin-coated pits	% of TfR-gold in clathrin-coated pits	Concentration of TfR-gold in clathrin-coated pits; fold
Control cells	1.1–1.4	8.7	∼7×
Cells treated for 30 min with 10 mM MβCD	1.4–1.8	11.5	∼7×

HEp-2 cells were fixed before incubation with 2 μg/ml B3/25 anti-TfR antibody. Forty large cell profiles (with a total of 2990 and 4812 golds, respectively) were included in the quantification from each experiment. 

^aData and calculations based on Hansen et al., 1992.