Membrane depolarization in NRK fibroblasts by bradykinin is mediated by a calcium-dependent chloride conductance.
The effects of the phosphoinositide-mobilizing agonist bradykinin (BK) on membrane potential and intracellular calcium in monolayers of normal rat kidney (NRK) fibroblasts were investigated. BK induced a rapid transient depolarization in these cells, which was mimicked by other phosphoinositide-mobilizing factors such as prostaglandin F2alpha (PGF2alpha), lysophosphatidic acid (LPA), platelet-derived growth factor (PDGF-BB), and serum. Depolarization by BK was independent of extracellular Ca2+ or Na+. It was shown using extracellular Cl- substitutions that the depolarization was caused by an increased Cl- conductance. Depolarization was inhibited by 5-nitro-2-3-phenylpropyl(amino)benzoic acid (NPPB), niflumic acid, and flufenamic acid, inhibitors of calcium-dependent chloride channels. The depolarization provoked by BK could be mimicked by raising intracellular calcium with ionomycin or thapsigargin and could be blocked with geneticin, a blocker of phospholipase C. When intracellular calcium was buffered by loading the cells with 1,2-bis(2-aminophenoxy)ethane-NNN'N'-tetra-acetic acid (BAPTA), depolarization was prevented. We conclude that in NRK fibroblasts extracellular stimuli that increase intracellular calcium, depolarize the cells via the activation of a calcium-dependent chloride conductance. In addition to an increase in intracellular calcium, depolarization may be an important effector pathway in response to extracellular stimuli in fibroblasts. It is hypothesized that, in electrically coupled cells such as NRK fibroblasts, intercellular transmission of these depolarizations may represent a mechanism to coordinate uniform multicellular responses to Ca2+-mobilizing agonists.
De Roos
A D
AD
Department of Cell Biology, University of Nijmegen, The Netherlands.
Van Zoelen
E J
EJ
Theuvenet
A P
AP
D000818:Animals; D000077214:Becaplermin; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism*; D015237:Dinoprost / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005347:Fibroblasts; D007668:Kidney; D007700:Kinetics; D008246:Lysophospholipids / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D013997:Time Factors
D018118:Chloride Channels; D002712:Chlorides; D008246:Lysophospholipids; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D000077214:Becaplermin; D004533:Egtazic Acid; D015237:Dinoprost; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D011188:Potassium; D001920:Bradykinin; D002118:Calcium