Effect of hypo-osmotic incubation on membrane recycling

✍ Scribed by Jeanne M. Novak; Diane McVey Ward; Saundra S. Buys; Jerry Kaplan

• Publisher: John Wiley and Sons
• Year: 1988
• Tongue: English
• Weight: 789 KB
• Volume: 137
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041370205

✦ Synopsis

Incubation of alveolar macrophages in hypo-osmotic media causes a time-and temperature-dependent increase in the number of surface receptors for three different ligands. Exposure of cells to solutions of 210 mOsM or less, at 37°C but not at o"C, resulted in an increase in the number of surface receptors for diferric transferrin, alpha-macroglobulin-protease complexes, and mannose-terminated glycoproteins. Upon media dilution at 37"C, surface receptor number reached a maximum within 5 min and returned to near-normal values by 30 min. The increase in surface receptor number was the result of a decrease in the rate of internalization of receptors, either occupied or unoccupied. The rate of receptor exteriorization was unaltered by hypo-osmotic incubation of cells. The rate of fluid-phase pinocytosis was also inhibited upon incubation in hypo-osmotic solution. In experiments in which both receptor-mediated endocytosis and fluid phase pinocytosis were measured on the same samples, inhibition of both processes occurred with the same kinetics and to a similar extent. The rate of receptor-rnediated endocytosis recovered to normal rates after 60 min in hypoosmotic solutions, whereas the rate of fluid phase pinocytosis did not recover to the same extent.