ABSTRACT
Berberine could reverse the phenylephrine-induced contraction of aortic strips of rabbits, but not those induced by histamine, serotonin and high-K. It showed no effect on the resting tension of the strips.Prazosin l ?M completely abolished the phenylephrine-induced contraction of the strips, but berberine 100 ?M could block 94 ? 9%.The IC50 of berberine and prazosin for phenylephrine-induced c-ontraction is 30 ?M and 0.2 ?M. The results suggest that the action of berberine is not similar to sodium nitroprusside, but is similar to prazosin, a selective ?1 adrenoceptor blocker, although its potency is less than prazosin.
ABSTRACT
The present experiments were designed to investigate the effects of atriopeptin I on different vascular smooth muscles.Isometric tension was recorded from spiral strips of human umbilical arteries, gastro-epiploica dextral arteries, rat and rabbit aorta. Atriopeptin H showed a potent inhibitor on the contraction induced by noradrenaline ( 3tmol/l), Serotonin ( lnmol/1), hista-mine ( 10M-mol/l ) and phenylephrine ( l(imol/l)in the strips of rat and rabbit aorta, but not on the contraction induced by the above-mentioned drugs and KC1 (80mmol/l), prostaglandine F2a ( 10umol /I) in umbilical and gastroepiploica dextral arteries of human beings. Sodium nitroprussids showed also a potent antagonist on the contraction induced by noradrenaline ( 3 M-mol/1) serotonin ( 1imol/l), histamine (10imol/1) and prostaglandine F2a (10nmol/l) in the strips of umbilical arteries.lt produced concentration-dependent inhibition of the contraction induced by noradrenaline.It could remarkably decrease the resting tension of the strips.The present results suggest that atriopeptin I exhibits a similar vasodilator profile in rat and rabbit aorta as that found for sodium nitroprusside in the human umbilical arteries.The ineffectiveness of atriopeptin I on human umbilicalj and gas-troepiploica dextral arteries is in marked contrast to the effectiveness of sodium nitroprusside in the human umbilical arteries, indicating that the action of atriopeptin f possesses species difference.
ABSTRACT
The effect of endothelin (ET-1) on the function of the isolated perfused working guinea pig has been examined. ET- 1 wasshowed to exert a transient positive inotropic effect on the isolated heart, followed by a marked inhibition of cardiac function. Low dose of ET- 1(30,90 pmol?L-1) produced reversible inhibition. The effect of high dose of ET- 1 was irreversible, accompanied with increasing LDH significantly, indomethacin markedly augmented the vasoconstrictor and cardiac ischemia effects of ET-1. Our results suggest that the apparent inhibition of cardiac function on the isolatedperfused guinea pig heart after administration of ET-1 may be due to the effect of the myocardial ischaemia caused by progressive development of coronary vasoconstriction. In our experimental model, PGI2 has partially antagonizing effect on the vasoconstrictor action of ET-1.