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Serum and α 2 ‐macroglobulin induce transient hyperpolarizations in the membrane potential of an osteoblastlike clone
Author(s) -
Dixon S. J.,
Aubin J. E.
Publication year - 1987
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041320205
Subject(s) - endocytosis , bovine serum albumin , intracellular , fetal bovine serum , membrane potential , microbiology and biotechnology , biophysics , receptor , biology , chemistry , cell culture , macroglobulin , receptor mediated endocytosis , biochemistry , cell , genetics
Using microelectrode techniques, we have observed that the application of serum or α 2 ‐macroglobulin (α 2 M) induces transient hyperpolarizations in the membrane potential of a rat osteosarcoma clone (ROS 17/2). Hyperpolarizations arose from activation of Ca 2+ ‐dependent K + channels by transient increases in the concentration of intracellular free Ca 2+ . Hyperpolarizing spikes were observed for several h following the addition of fetal bovine serum (FBS) to cell cultures. Application of small volumes of FBS or α 2 M rapidly induced synchronized bursts of hyperpolarizing spikes. No response was elicited by serum‐free medium, latex beads, or bovine serum albumin (BSA). Immunofluorescence labeling patterns were consistent with the receptor‐mediated endocytosis of α 2 M but not BSA. The ligand specificity and kinetics of these hyperpolarizations suggest that they are associated with a receptor‐mediated event, possibly an early stage of receptor‐mediated endocytosis.