title: Effect of bradykinin on the cytosolic free calcium activity and phosphoinositol turnover in human glomerular epithelial cells.
abstract: The effect of bradykinin (BK) on the intracellular free calcium activity [Ca2+]i and phosphoinositide (PI) turnover was investigated in human glomerular epithelial cells (GEC) in culture. Human GEC exhibited a baseline [Ca2+]i of 114 +/- 3 nmol (n = 81). BK (ED50 10(-9) mol/l) caused a rapid and transient increase in [Ca2+]i, which could also be observed in the absence of extracellular calcium. The effect of BK (10(-8) mol/l) on the [Ca2+]i was inhibited by the BK2 antagonist Hoe 140 (IC50 10(-8) mol/l). BK also induced PI turnover in a time- and dose-dependent manner. A transient increase in (1,4,5)-inositol-triphosphate (InsP3) formation from 1,445 +/- 119 to 4,629 +/- 323 cpm occurred after 5 s. Stimulation of protein kinase C (PKC) by short-term preincubation (15 min) of human GEC with phorbol-12-myristate-13-acetate (PMA) induced a dose-dependent inhibition of the BK-stimulated (10(-7) mol/l) inositol-phosphate formation. Downregulation of PKC by preincubation of human GEC with PMA (24 h, 10(-6) mol/l) or inhibition of PKC by pretreatment with staurosporin (1 h, 10(-6) mol/l) resulted in a slight but significant augmentation of the BK-induced InsP3 stimulation. The data indicate that BK induces stimulation of [Ca2+]i and PI turnover via a BK2 receptor in human GEC. PKC might exert a negative feedback function for the BK-induced PI turnover.
mesh_terms: D001920:Bradykinin / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D005246:Feedback; D006801:Humans; D007678:Kidney Glomerulus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D010716:Phosphatidylinositols; C065679:icatibant; D011493:Protein Kinase C; D001920:Bradykinin; D002118:Calcium