[Mechanism of action of parathyroid hormone on the functional activity of myocardial tissue].

The effect of the parathyroid hormone (PTH) on AP and the ventricle myocardium contractions in frogs was studied under conditions of the calcium permeability blockade and in calciumfree solution: the AP duration shortened, while AP amplitude increased like in control solution. The hormone's ion mechanisms are supposed to be based on increased transfer of calcium along the "slow" channels of membrane and of sodium--along the "fast" channels, as well as on activation of the Na-K-dependent ATPhase.