Table 2.

Distribution of TfR, Tf, GHR, and GH over the limiting membrane of early endosomal vacuoles of wtGHR cells

	Coated areas	Noncoated areas	Nondefined
A Labeling (%)
TfR	9.1  ± 1.7	77.3  ± 5.6	13.6  ± 4.3
Tf	8.8  ± 1.8	74.6  ± 1.3	16.6  ± 0.7
GHR	24.4  ± 4.4	60.7  ± 1.9	14.9  ± 3.1
GH	21.2  ± 4.2	59.7  ± 5.1	19.1  ± 1.3
B Surface area (%)	11.3	74.7	14.0
C Labeling surface ratio
TfR	0.8	1.0	1.0
Tf	0.8	1.0	1.2
GHR	2.2	0.8	1.1
GH	1.9	0.8	1.4

WtGHR cells were allowed to internalize biotinylated GH or -Tf for 30 min and labeled for biotin, TfR, or GHR. (A) Numbers represent the percentage of total gold label (±SD) of the indicated protein found over the subdomains of the limiting membrane of the EE vacuole. Areas of the membrane that were not clearly visible in the cross section are referred to as nondefined. (B) Relative contributions of coated and noncoated membrane areas to the total of the endosomal limiting membrane are indicated as percentages. (C) Labeling surface ratio of a given protein in either of the endosomal subdomains was calculated by dividing the percentage of total label in one subdomain by the percentage of membrane that is occupied by this subdomain (n = 50 endosomes). A ratio >1.00 indicates an increase and <1.00 a decrease in labeling density compared with a random distribution of a protein over the endosomal limiting membrane.