Phenylarsine oxide-induced increase in alveolar macrophage surface receptors: Evidence for fusion of internal receptor pools with the cell surface

Abstract

Rabbit alveolar macrophages which were treated at 0°C with phenylarsine oxide and then incubated at 37°C for 10 rain exhibited a two- to threefold increase in surface receptor activity for macroglobulin.protease complexes, diferric transferrin, and mannoseterminal glycoproteins. Analysis of the concentration-dependence of ligand binding indicated that changes in ligand-binding activity were due to changes in receptor number rather than alterations in ligand-receptor affinity. Surface receptor number could also be increased by treatment of cells with three other sulfhydryl reagents, N-ethylmalemide, p-chloromercurobenzoate, and iodoacetic acid. The increase in receptor activity was maximal after 10 min and decreased over the next hour. This decrease in cell-associated receptor activity was due to the release of large membrane vesicles which demonstrated a uniform buoyant density by isopycnic sucrose gradient centrifugation. Treatment of cells with phenylarsine oxide did not decrease the cellular content of lactate dehydrogenase or β-galactosidase, indicating that cell integrity was maintained and lysosomal enzyme release did not occur. Our studies indicate that phenylarsine oxide treatment in the presence of extracellular Ca2+ results in the fusion of receptor-containing vesicles with the cell surface. © 1985, Rockefeller University Press., All rights reserved.