Receptors for transferrin and transcobalamin II display segregated distribution on microvilli of leukemia L1210 cells.

Simultaneous addition of uniform latex particles derivatized with transferrin (0.532 micron) and transcobalamin II (0.345 micron) to leukemia L1210 cells resulted in segregated binding to individual microvilli as demonstrated by scanning electron microscopy. This segregated distribution suggests that individual microvilli are endowed either transferrin or transcobalamin II receptors but not both. Intracellular sorting and segregation of newly synthesized or recycling receptors probably occur prior to expression on the plasmalemma microvilli.