title: Mechanisms involved in carbachol-induced Ca(2+) sensitization of contractile elements in rat proximal and distal colon.
abstract: 1. Mechanisms involved in Ca(2+) sensitization of contractile elements induced by the activation of muscarinic receptors in membrane-permeabilized preparations of the rat proximal and distal colon were studied. 2. In alpha-toxin-permeabilized preparations from the rat proximal and distal colon, Ca(2+) induced a rapid phasic and subsequent tonic component. After Ca(2+)-induced contraction reached a plateau, guanosine 5'-triphosphate (GTP) and carbachol (CCh) in the presence of GTP further contracted preparations of both the proximal and distal colon (Ca(2+) sensitization). Y-27632, a rho-kinase inhibitor, inhibited GTP plus CCh-induced Ca(2+) sensitization more significantly in the proximal colon than in the distal colon. 3. Y-27632 at 10 microm had no effect on Ca(2+)-induced contraction or slightly inhibited phorbol-12,13-dibutyrate-induced Ca(2+) sensitization in either proximal or distal colon. Chelerythrine, a protein kinase C inhibitor, inhibited GTP plus CCh-induced Ca(2+) sensitization in the distal colon, but not in the proximal colon. The component of Ca(2+) sensitization that persisted after the chelerythrine treatment was completely inhibited by Y-27632. 4. In beta-escin-permeabilized preparations of the proximal colon, C3 exoenzyme completely inhibited GTP plus CCh-induced Ca(2+) sensitization, but PKC(19-31) did not. In the distal colon, C3 exoenzyme abolished GTP-induced Ca(2+) sensitization. It inhibited CCh-induced sensitization by 50 % and the remaining component was inhibited by PKC(19-31). 5. These results suggest that both protein kinase C and rho pathways in parallel mediate the Ca(2+) sensitization coupled to activation of muscarinic receptors in the rat distal colon, whereas the rho pathway alone mediates this action in the proximal colon.
authors.affiliation: Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Science, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai Osaka 599-8531, Japan. takeuchi@vet.osakafu-u.ac.jp
authors.forename: Tadayoshi
authors.initials: T
authors.lastname: Takeuchi
authors.forename: Masahiko
authors.initials: M
authors.lastname: Kushida
authors.forename: Nobue
authors.initials: N
authors.lastname: Hirayama
authors.forename: Muneyoshi
authors.initials: M
authors.lastname: Kitayama
authors.forename: Akikazu
authors.initials: A
authors.lastname: Fujita
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Hata
mesh_terms: D036002:ADP Ribose Transferases / Q000494:pharmacology; D000470:Alkaloids; D000577:Amides / Q000494:pharmacology; D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology; D053119:Benzophenanthridines; D001905:Botulinum Toxins / Q000494:pharmacology; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002217:Carbachol / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002463:Cell Membrane Permeability / Q000187:drug effects; D044682:Colon, Ascending / Q000187:drug effects* / Q000473:pathology; D044683:Colon, Descending / Q000187:drug effects* / Q000473:pathology; D004928:Escin / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000037:antagonists & inhibitors / Q000494:pharmacology; D006460:Hemolysin Proteins / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D007564:Japan; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000502:physiology; D010446:Peptide Fragments / Q000494:pharmacology; D010617:Phenanthridines / Q000037:antagonists & inhibitors / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011976:Receptors, Muscarinic / Q000187:drug effects; D014316:Tritium; D010738:Type C Phospholipases / Q000494:pharmacology; D054460:rho-Associated Kinases
chemical_list: D000470:Alkaloids; D000577:Amides; D001427:Bacterial Toxins; D053119:Benzophenanthridines; D006460:Hemolysin Proteins; D047908:Intracellular Signaling Peptides and Proteins; D010446:Peptide Fragments; D010617:Phenanthridines; D011725:Pyridines; D011976:Receptors, Muscarinic; C073885:protein kinase C (19-31); C021091:staphylococcal alpha-toxin; D014316:Tritium; C108830:Y 27632; D015240:Phorbol 12,13-Dibutyrate; D004928:Escin; D006160:Guanosine Triphosphate; D002217:Carbachol; C016299:chelerythrine; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D010738:Type C Phospholipases; D001905:Botulinum Toxins; D002118:Calcium