title: Investigation into vanadate-induced potentiation of smooth muscle contractility in the rabbit isolated ileum.
abstract: The action of sodium orthovanadate (Na3VO4) on spontaneous mechanical activity of the longitudinal muscle was investigated in isolated segments of rabbit distal ileum. Vanadate (0.3-1000 microM) concentration-dependently enhanced the amplitude of phasic contractions (pendular movements) and caused the muscle tone to slightly increase at the highest concentrations. Both these effects were mimicked by the Ca2+ channel activator BAY K 8644 (10-1000 nM). Vanadate- and BAY K 8644-induced potentiation of mechanical activity was antagonized by the Ca2+ entry blocker nifedipine (3 nM). In Ca(2+)-free, K(+)-depolarized preparations, vanadate (100 microM) failed to contract the musculature, but potentiated the contractile response to applied calcium (CaCl2: 30-300 microM). The action of vanadate was similar to that of BAY K 8644 (3 nM) and was antagonized by nifedipine (0.1 nM). These results suggest that extracellular calcium is required for vanadate-induced smooth muscle excitation which, at least in part, appears to arise from facilitation of calcium influx through voltage-dependent Ca2+ channels.
authors.affiliation: Department of Internal Medicine and Therapeutics, University of Pavia, Italy.
authors.forename: S M
authors.initials: SM
authors.lastname: Candura
authors.forename: L
authors.initials: L
authors.lastname: Manzo
authors.forename: P
authors.initials: P
authors.lastname: Marraccini
authors.forename: T
authors.initials: T
authors.lastname: Coccini
authors.forename: M
authors.initials: M
authors.lastname: Tonini
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D005260:Female; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D011817:Rabbits; D014638:Vanadates / Q000494:pharmacology*
chemical_list: D015220:Calcium Channels; D014638:Vanadates; D002118:Calcium