[Activating effect of lanthanum on the isolated coronary artery]

In isolated bovine coronary arteries after preceding calcium depletion by EGTA, lanthanum causes a reversible contracutre that is independent of the presence of extracellular calcium. Also, the contracture appears to be widely independent of intracellular calcium. In the superprecipitation reaction of isolated actomyosin from bovine carotis, lanthanum ions can be substituted for calcium ions. The lanthanum contracture relies either on mobilization of intracellular calcium, or on direct interaction of lanthanum ions with the contractile proteins. In both cases it has to be assumed that lanthanum penetrates into the cell.