Interaction between lanthanum and calcium in isolated guinea-pig heart

The effect of lanthanum ion on the contraction of the perfused guinea-pig heart has been investigated. Lanthanum caused inhibition of the contractile force. The dose-response curves suggest that there is more than one site with which lanthanum may interact. The high affinity interaction is antagonised by high external calcium. The possibility that a low concentration of lanthanum may block calcium entry into the myocardium is discussed.