Antagonism of calcium by zinc in guinea-pig isolated taenia caeci and trachealis muscle.
1 In guinea-pig isolated taenia caeci and trachealis bathed in a K+-rich, Ca2+-free medium, CaCl2 (0.01-10 mM) produced a concentration-dependent contraction. Zn2+ (0.01-1 mM), Cd2+ (0.01-1 mM), verapamil (0.01-100 microM) and trifluoperazine (1-100 microM) were effective antagonists of CaCl2-induced responses. 2 Zn2+ and Cd2+ in concentrations from 0.01 to 1 mM were without effect on the tone of taenia and trachea in normal Tris solution. Conversely, Zn2+ and Cd2+, in concentrations of 1 mM, caused contraction of these tissues in a K+-rich, Ca2+-free medium. Zn2+ (1 mM)-induced contractions of taenia and trachea were completely inhibited by verapamil (10 microM). 3 In taenia and trachea skinned of their plasma membranes, tension development induced by Ca2+ (10 microM or 1 microM, respectively) was unaffected by verapamil (100 microM), whereas trifluoperazine (100 microM) depressed the maximal tension produced by Ca2+. Segments of skinned preparations contracted in response to low concentrations of Zn2+ (10 microM) or Cd2+ (10 microM). 4 It is concluded that Zn2+ may suppress Ca2+-induced spasm by a direct action on the binding sites of the Ca2+ channel.
Sarriá
B
B
Department de Farmacología y Farmacotecnia, Facultat de Medicina, Universitat de València, Spain.
Cortijo
J
J
Martí-Cabrera
M
M
Morcillo
E
E
Esplugues
J
J
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000037:antagonists & inhibitors*; D002432:Cecum / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects*; D014132:Trachea / Q000187:drug effects; D014268:Trifluoperazine / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology*
D002104:Cadmium; D014268:Trifluoperazine; D014700:Verapamil; D015032:Zinc; D000109:Acetylcholine; D002118:Calcium