Axial heterogeneity of organic cation transport along the rabbit renal proximal tubule: studies with brush-border membrane vesicles.

Brush-border membrane vesicles prepared from rabbit kidney outer cortex (rich in S1 and S2) and outer medulla (rich in S3) were used to evaluate the axial heterogeneity of tetraethylammonium transport in the proximal tubule. The vesicle preparations had similar Km values but the Vmax values differed, suggesting that axial heterogeneity of tetraethylammonium secretion may be due to differences in transport across the brush-border membrane.