[Cryolabile calcium and contractility of rat auricle]

Cooling to 2 degrees C during 15 minutes rat auricles immersed into a calcium free Krebs-Ringer solution induced extrusion of intracellular calcium. the quantity of extruded calcium is able to restore the rythmic contractility of new auricles immersed in this medium when rewarmed to 37 degrees C. Apparently this calcium is not involved in the mechanism of muscular contraction and this liberation does not seem to be related to an inhibition of Na-K . ATPase coupled to the Na/Ca exchange.