[Effects of sodium molybdate on guinea pig atria contractility]

Sodium molybdate (Mo) 10-1000 mumol/L markedly reduced the contratile force of left atria isolated from guinea pig. Mo 100 mumol/L obviously reduced the heart rates in right atria, markedly prolonged the functional refractory period from 185 +/- 12 to 245 +/- 4 ms and inhibited the resting potentiation. Mo 100 and 300 mumol/L reduced the frequency-dependent positive staircase phenomenon. However, verapamil 25 mumol/L reversed the frequency-dependent positive staircase phenomenon to negative one. The mechanism can be explained by the effect on Ca2+ movement in the heart atrium.