title: Selective involvement of calcium and calcium channels in stimulated mucin secretion from rat colon.
abstract: BACKGROUND
  The cellular mechanisms involved in the mucin secretion of rat colon are unknown. The objective of the present study was thus to determine the role of extracellular calcium and of L-type calcium channels in rat intestinal mucin discharge.
  
  
  METHODS
  The experiments were conducted using the isolated vascularly perfused rat colon. Mucin secretion was evaluated using an enzyme-linked immunosorbent assay.
  
  
  RESULTS
  Intra-arterial bethanechol (200 microM) or luminal deoxycholate (5 mM) produced a significant mucin discharge (609% and 386% of controls, respectively). The colonic mucin output induced by these two secretagogues was significantly inhibited by arterial administration of EGTA (2 mM), verapamil (100 microM) or nifedipine (50 microM). In contrast, luminal EGTA (2 mM) had no inhibitory effect. Intra-arterial infusion of the calmodulin antagonist trifluoperazine (10 microM) also reduced mucin discharge induced by bethanechol or deoxycholate (304% and 223% of controls, respectively). Colonic mucin secretion was significantly stimulated after intra-arterial infusion of 3-isobutyl-methylxanthine (IBMX, 100 microM) or forskolin (2-20 microM). Stimulation by forskolin was unaffected by arterial EGTA, verapamil, nifedipine or trifluoperazine.
  
  
  CONCLUSIONS
  In the isolated vascularly perfused rat colon, mucin discharge induced by bethanechol or deoxycholate requires extracellular calcium and the activation of voltage-dependent calcium channels of L-type. In contrast, forskolin does not appear to stimulate mucin release by increasing calcium entry.
authors.affiliation: INSERM U45, Hôpital Edouard Herriot, Lyon, France.
authors.forename: A
authors.initials: A
authors.lastname: Barcelo
authors.forename: J
authors.initials: J
authors.lastname: Claustre
authors.forename: J
authors.initials: J
authors.lastname: Abello
authors.forename: J A
authors.initials: JA
authors.lastname: Chayvialle
authors.forename: P
authors.initials: P
authors.lastname: Plaisancié
mesh_terms: D000818:Animals; D018723:Bethanechol / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000502:physiology*; D003106:Colon / Q000187:drug effects / Q000378:metabolism*; D003840:Deoxycholic Acid / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D008297:Male; D009077:Mucins / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D009077:Mucins; D018723:Bethanechol; D003840:Deoxycholic Acid; D002118:Calcium