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正

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Effects of iodium-heterocyclic compound（IHC-64）on physiologicalproperties of guinea pig papillary muscles were reported.IHC-64 not onlydepressed the myocardiac contraction with IC

50

119.4±10.9μm

but also prolongedthe effective refractory period（ERP）from 190.5±13.9ms to 202.0±13.6 ms（P

<

0.01）.Moreover

it increased the concentration for adrenaline to induceautomaticity of the papillary muscles by 2.8±1.1 folds（P

<

0.01）without markedeffects on its excitability.IHC-64 reduced significantly the contractility inducedby isoprenaline in potassium-depolarized guinea pig papillary muscles

makingthe isoprenaline dose-effect curves shift in a non-parallel manner.These resultsdemonstrate preliminarily that IHC-64 may be a new calcium antagonist.