title: Bradykinin contracts rat urinary bladder largely independently of phospholipase C.
abstract: Several receptor systems in the bladder causing detrusor smooth muscle contraction stimulate phospholipase C (PLC). PLC inhibition abolishes bladder contraction via P2Y6 but not that via M3 muscarinic receptors, indicating a receptor-dependent role of PLC. Therefore, we explored the role of PLC in rat bladder contraction by bradykinin. The PLC inhibitor U 73,122 [1-(6-[([17β]-3-methoxyestra-1,3,5[10]-trien-17-yl)-amino]hexyl)-1H-pyrrole-2,5-dione] did not affect the bradykinin response to a significantly greater degree than its inactive analog U 73,343 [10 μM each; 1-(6-[-([17β]-3-methoxyestra-1,3,5[10]-trien-17-yl)-amino]hexyl)-2,5-pyrrolidinedione], whereas the phospholipase D inhibitor butan-1-ol relative to its inactive control butan-2-ol caused a weak but significant inhibition (0.3% each). The cytosolic phospholipase A2 inhibitor arachidonyltrifluoromethyl ketone (300 μM) and the cyclooxygenase inhibitor indomethacin (10 μM) caused strong inhibition of the bradykinin response. The L-type Ca(2+) channel blocker nifedipine (10-100 nM) concentration-dependently caused strong inhibition, whereas only a small but significant inhibition was seen with SK&F 96,365 [10 μM; 1-[β-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole HCl], an inhibitor of receptor-operated Ca(2+) channels. Several protein kinase C inhibitors yielded an equivocal picture (inhibition by 10 μM bisindolylmaleimide I and 1 μM calphostin but not by 10 μM chelerythrine). The rho kinase inhibitor Y 27,632 [1-10 μM; trans-4-[(1R)-1-aminoethyl]-N-4-pyridinylcyclohexanecarboxamide] caused a strong and concentration-dependent inhibition of the bradykinin response. Our data support that not only M3 but also bradykinin receptors cause bladder contraction by a largely PLC-independent mechanism. Both responses strongly involve L-type Ca(2+) channels and rho kinase, whereas only the bradykinin response additionally involves the phospholipase A2/cyclooxygenase pathway.
authors.affiliation: Department of Pharmacology, University of Duisburg-Essen, Essen, Germany (C.S.); and Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany (M.C.M.).
authors.forename: Carsten
authors.initials: C
authors.lastname: Sand
authors.forename: Martin C
authors.initials: MC
authors.lastname: Michel
mesh_terms: D000818:Animals; D001920:Bradykinin / Q000494:pharmacology / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology*; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000502:physiology*; D001743:Urinary Bladder / Q000187:drug effects / Q000201:enzymology*
chemical_list: D010738:Type C Phospholipases; D001920:Bradykinin