title: A possible explanation for effects of Sr2+ on contraction-relaxation cycle in canine stomach.
abstract: Effects of Sr2+ on smooth muscle activity and Ca2+ movement by plasma membrane (PM) were examined in preparations isolated from canine stomach to determine how Sr2+ modulates the contraction-relaxation cycle in smooth muscle. Sr2+ caused contraction in Ca2+-free solution. In the presence of Sr2+, KCl caused a response similar to that in normal Ringer's solution, this contraction was inhibited by both nitroprusside and verapamil. Sr2+ inhibited Ca2+ uptake by PM in the presence and absence of ATP. Release of Ca2+ from loaded PM vesicles was accelerated by Sr2+. Results suggest that Sr2+ could replace Ca2+ in Ca2+ binding sites in the cell.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D004285:Dogs; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects; D009599:Nitroprusside / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D013270:Stomach / Q000502:physiology*; D013324:Strontium / Q000494:pharmacology*; D014700:Verapamil / Q000494:pharmacology
chemical_list: D009599:Nitroprusside; D011189:Potassium Chloride; D000255:Adenosine Triphosphate; D002217:Carbachol; D014700:Verapamil; D002118:Calcium; D013324:Strontium