Crosslinking of the receptors for immunoglobulin E depolarizes the plasma membrane of rat basophilic leukemia cells.

Abstract

Aggregation of the receptor for IgE on mast cells, basophils, and a tumor analog, rat basophilic leukemia (RBL) cells, induces a Ca-dependent degranulation of the cells. The membrane potential (.DELTA..PSI.) of RBL cells was measured during this reaction by using the tetraphenylphosphonium ion (Ph4P+) equilibration technique. A 20-45% reduction in ionophore-sensitive Ph4P+ accumulation was noted. The phenomenon persisted under conditions expected to collapse the mitochondrial .DELTA..PSI. consistent with the effect being due to a change in .DELTA..PSI. of the plasma membrane. The change may reflect a depolarization of 20 mV (from -90 to -70 mV, interior negative). While degranulation fails to occur in the absence of external Ca2+, this was not true of the depolarization, indicating that the latter was not a consequence of secretion. When aggregation of the receptor is induced by reaction of the cell-bound IgE with a multivalent antigen, the secretory reaction can be halted by adding a univalent hapten. In this case, complete repolarization occurs. Equivalent depolarization was observed in the absence of Na+ but was diminished when both Ca2+ and Na+ were absent. Apparently, aggregation of the receptor opens ion channels, and the latter disappear promptly when the receptors are disaggregated. Formation of these channels may lead to the entry of Ca2+ and be an early and critical consequence of the aggregation of the receptors, thereby leading to degranulation.