Significance of Na ions in determining the effect of Ca ions on the frog heart.
D000818:Animals; D001001:Anura; D002118:Calcium / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects*; D012964:Sodium / Q000494:pharmacology*; D012965:Sodium Chloride / Q000494:pharmacology*
D012965:Sodium Chloride; D012964:Sodium; D002118:Calcium