Signal transduction underlying carbachol-induced contraction of rat urinary bladder. I. Phospholipases and Ca2+ sources.
We have reexamined the muscarinic receptor subtype mediating carbachol-induced contraction of rat urinary bladder and investigated the role of phospholipase (PL)C, D, and A2 and of intra- and extracellular Ca2+ sources in this effect. Based on the nonsubtype-selective tolterodine, the highly M2 receptor-selective (R)-4-[2-[3-(4-methoxy-benzoylamino)-benzyl]-piperidin-1-ylmethyl]-piperidine-1-carboxylic acid amide (Ro-320-6206), and the highly M3 receptor-selective darifenacin and 3-(1-carbamoyl-1,1-diphenylmethyl)-1-(4-methoxyphenylethyl)pyrrolidine (APP), contraction occurs via M3 receptors. Carbachol stimulated inositol phosphate formation in rat bladder slices, and this was abolished by the phospholipase C inhibitor 1-(6-[([17beta]-3-methoxyestra-1,3,5[10]-trien-17-yl)-amino]hexyl)-1H-pyrrole-2,5-dione (U 73,122; 10 microM). Nevertheless, U 73,122 (1-10 microM) did not significantly affect carbachol-stimulated bladder contraction. Carbachol had only little effect on PLD activity in bladder slices, but the PLD inhibitor butan-1-ol, relative to its negative control butan-2-ol (0.3% each), caused detectable inhibition of carbachol-induced bladder contraction. The cytosolic PLA2 inhibitor arachidonyltrifluoromethyl ketone weakly inhibited carbachol-induced contraction at a concentration of 300 microM, but the cyclooxygenase inhibitor indomethacin (1-10 microM) remained without effect. The Ca2+ entry blocker nifedipine (10-100 nM) almost completely inhibited carbachol-induced bladder contraction. In contrast, 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole HCl (SKF 96,365; 10 microM), an inhibitor of store-operated Ca2+ channels, caused little inhibition. We conclude that carbachol-induced contraction of rat bladder largely depends on Ca2+ entry through nifedipine-sensitive channels and, perhaps, PLD, PLA2, and store-operated Ca2+ channels, whereas cyclooxygenase and, surprisingly, also PLC are not involved to a relevant extent.
Schneider
Tim
T
Department of Medicine, University of Essen, Germany.
Hein
Peter
P
Michel
Martin C
MC
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology*; D005260:Female; D010739:Phospholipase D / Q000378:metabolism / Q000502:physiology; D010740:Phospholipases / Q000502:physiology*; D010741:Phospholipases A / Q000378:metabolism / Q000502:physiology; D054467:Phospholipases A2; D011451:Prostaglandin-Endoperoxide Synthases / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology*; D010738:Type C Phospholipases / Q000378:metabolism / Q000502:physiology; D001743:Urinary Bladder / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D014590:Uterine Contraction
D002217:Carbachol; D011451:Prostaglandin-Endoperoxide Synthases; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; D010739:Phospholipase D; D002118:Calcium