Objective: To study the adjustment mechanism of tea pigments (TP) on isolated toad myocardial contraction. Method: Toads were randomly assigned to the control groups and the experimental groups

the control groups were then divided into the normal Ringer solution group

the negative group

the positive group and the drug group. The normal Ringer solution group received Ringer solution only

the negative groups received low calcium Ringer solution following Ringer solution

the positive group received high calcium Ringer solution following Ringer solution and the drug group received TP

verapamil

atropine or isopropyl epinephrine solution

respectively

following Ringer solution. The effects on specimens of isolated toad hearts were observed. The experimental groups were divided into the verapamil group

the atropine group and the isopropyl adrenaline. All drug groups in the experimental groups included the low calcium and high calcium groups

and the low calcium and high calcium group was then divided into two groups as before or after TP-adding of 8 toads each. The perfusion specimens of isolated toad heart were prepared by Si's method. The specimens were perfused by verapamil (7.27 mg·L-1)

atropine (10 mg·L-1) and isoproterenol (10 mg·L-1) before or after TP adding (200 mg·L-1). The toad myocardial contraction curves were recorded by using BL-420F biological function in vitro experimental system

and the myocardial contractility was analyzed statistically. Result: Myocardial contractility increased when perfusing low calcium and inhibited when perfusing high calcium (P<0.05)

and it could be blocked partially by verapamil and stimulated by isoprenaline (P<0.01). It had both cooperation and antagonism on atropine (P<0.05). Conclusion: The protective effect of TP on isolated toad heart may be associated with calcium channels

M receptor and β receptor.