IKir regulation in murine macrophages: whole cell and perforated patch studies
Judge, S.I.; Montcalm-Mazzilli, E.; Gallin, E.K.
American Journal of Physiology 267(6 Pt 1): C1691-C1698
1994
ISSN/ISBN: 0002-9513 PMID: 7810612 Document Number: 432485
Previous studies have reported that the inwardly rectifying K+ conductance (G-Kir) in macrophages is modulated by intracellular perfusion with inositol 1,4,5-trisphosphate (InsP-3), inositol 1,3,4,5-tetrakisphosphate (InsP-4), or GTP analogues and by exposing cells to macrophage-specific colony-stimulating factor (CSF) I. This study uses both conventional whole cell and amphotericin B perforated patch studies to investigate G-Kir modulation in thioglycollate-elicited mouse peritoneal macrophages (M-THETA). Under whole cell recording conditions with 150 mM Cl- in the patch pipette, G-Kir decreased within 25 min. The G-Kir decrease was slowed by exchanging glutamate for Cl- as the major anion in the pipette or by adding guanosine 5'-O-(2-thiodiphosphate) (50 nM) or ATP (0.5 mM) to the pipette. Addition of InSP-3 or InSP-4 to the pipette had no effect on the magnitude of G-Kir or its rate of decrease but activated an outward current in the voltage range of +60 to +120 mV in 57% of the cells studied. Thus in murine M-THETA G-Kir may be modulated by G proteins but is unaffected by inositol phosphate metabolites, which have been reported to enhance G-Kir in phorbol 12-myristate 13-acetate (PMA)-differentiated HL-60 cells. In contrast to whole cell studies, perforated patch recordings of murine M-THETA G-Kir were stable for gt 1 h. Perforated patch studies demonstrated that murine M-THETA also differ from PMA-differentiated HL-60 cells in that CSF I had no effect on G-Kir. Additionally, arachidonic acid, PMA, and H-2O-2, agents implicated in macrophage activation, did not modulate G-Kir. We conclude that G-Kir regulation in murine M-THETA differs from that reported in PMA-differentiated HL-60 cells and that although our data suggest that G-Kir is modulated by G protein(s), they differ from the G proteins involved in M-THETA responses to CSF I and the other agents tested.