title: Effects of calcitonin gene-related peptide on intracellular calcium concentration in longitudinal muscle of guinea pig ileum.
abstract: The effect of rat calcitonin gene-related peptide (rCGRP) on intracellular free calcium concentration ([Ca2+]i) and its relationship with muscle relaxation were examined in plexus-free longitudinal muscle (LM) of the guinea pig ileum using a [Ca2+]i-tension simultaneous recording technique. Tissue was stimulated with either histamine (0.5 microM) or KCl (30 mM). rCGRP at a concentration of 263 nM (which displayed maximal relaxation of the LM) caused a small and brief but significant decrease in the [Ca2+]i in histamine-treated tissue. On the other hand, the same concentration of rCGRP relaxed the muscle without affecting the [Ca2+]i in KCl-treated tissue. rCGRP caused a dissociation between the changes in [Ca2+]i and tension. The effects of forskolin 0.5 microM) and nifedipine (10 nM) on both [Ca2+]i and tension were examined in comparison with rCGRP. Forskolin lowered the tension to greater extent than the [Ca2+]i whereas nifedipine (10 nM) diminished both the [Ca2+]i and tension in a parallel manner in histamine-treated tissues. These results suggest that rCGRP may not reduce [Ca2+]i as its primary mechanism of relaxation and it may change the calcium sensitivity of the contractile elements of the smooth muscle.
authors.affiliation: Department of Physiology, University of Alberta Faculty of Medicine, Edmonton, Canada.
authors.forename: Y D
authors.initials: YD
authors.lastname: Sun
authors.forename: C G
authors.initials: CG
authors.lastname: Benishin
mesh_terms: D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology; D007082:Ileum / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D066298:In Vitro Techniques; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009197:Myenteric Plexus / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D012044:Regression Analysis; D013997:Time Factors
chemical_list: D011189:Potassium Chloride; D006632:Histamine; D009543:Nifedipine; D015740:Calcitonin Gene-Related Peptide; D002118:Calcium