Inward rectification in mouse macrophages: evidence for a negative resistance region

Abstract

The electrical properties of cultured mouse thioglycollate-induced peritoneal macrophages were investigated using intracellular recording techniques. Thirty-five percent of the cells studied had membrane potentials ranging from -65 to -95 mV and exhibited S-shaped, steady-state current-voltage (I-V) relationships containing a transitional region. Analysis of currents in the transitional region from the rate of rise and fall of the voltage responses to current pulses indicated the presence of a negative resistance region in this area. Tetrodotoxin (3 X 10(-5) M), cobalt chloride (3 mM), 4-aminopyridine (4 mM), and tetraethylammonium chloride (8 mM) did not eliminate the transitional region of the I-V curves, whereas addition of barium chloride (4 mM) and rubidium chloride (3 mM) did. Increasing the external concentration of potassium shifted the I-V relationship horizontally along the current axis but did not eliminate the transitional region. These data indicate that the inward rectification and the negative resistance region probably result from a voltage-dependent potassium conductance.

Extracellular ATP induces a large nonselective conductance in macrophage plasma membranes.

“…4B, measured at three different [ATP]. In the absence of ATP, the expression of the inward rectifying K+ conductance is evident (13). At 100 ,uM ATPt, the inward rectifier was partly counterbalanced by the ATP conductance, which caused the bistability in membrane potential (13) at low [ATP] (cf.…”

Differential Voltage-dependent K+ Channel Responses during Proliferation and Activation in Macrophages

“…Lanes 1,3,5,7,9, and 10, PCR reactions from BMDM. Lanes 2,4,6,8,11, PCR from mouse brain. Lane 9 of Kv1.5 is a negative control in the absence of the RT reaction.…”

Clustering of very late antigen-4 integrins modulates K+ currents to alter Ca2+-mediated monocyte function

“…Human monocytic leukemia THP-1 cells exhibit many of the K ϩ conductances present in normal monocytes and macrophages (11,18), one of which, the I ir , when present sets the RMP to more negative levels. However, in the current study, the majority of THP-1 monocytes with clustered VLA-4 integrins also expressed a I dr , and this K ϩ current contributed to RMP by driving RMP toward its threshold activation voltage of Ϫ45 mV.…”

“…In most cells the presence of an I ir sets RMP close to the equilibrium potential for K ϩ (E K ) in the range of Ϫ55 to Ϫ85 mV (14,18,26). In fact, there were several individual THP-1 monocytes adherent to VCAM-1 or MAbVLA-4x possessing RMP of Ϫ55 mV or greater in which I ir was the predominant current (Fig.…”