title: Samarium as a tool in studies on the responsiveness of the isolated guinea pig ventral taenia coli to barium.
abstract: The responsiveness of isolated guinea pig ventral taenia coli to barium in polarized (Ringer-Tris medium) and depolarized (Ringer-KCl medium) preparations was assayed in the presence of samarium (Sm3+, 6 or 8 X 10(5) M). No difference in EC50 or maximal response was observed between polarized and depolarized preparations (p greater than 0.05). The lower Sm3+ concentration increased Ba2+ EC50 in both experimental conditions (p less than 0.05) although no alteration was observed as to the maximal response (p greater than 0.05). On the other hand, maximal tension was strongly reduced by the higher Sm3+ concentration in polarized preparations (p less than 0.01) while a potentiation of the maximum response was observed on the depolarized tissues (p less than 0.05). A possible role for calcium ions in the mediation of the effects is suggested.
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology*; D003106:Colon / Q000187:drug effects*; D004573:Electrolytes; D006168:Guinea Pigs; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects; D010477:Perfusion; D012493:Samarium / Q000494:pharmacology*
chemical_list: D004573:Electrolytes; D001464:Barium; D012493:Samarium