Contractile effects of jellyfish toxin extracted from Carybdea rastonii on isolated rabbit aorta

Effects of the toxic component of jellyfish (Carybdea rastonii) (pCrTX) on the smooth muscle tension of isolated rabbit thoracic aorta were examined. pCrTX, at concentrations higher than 10(-7) g/ml, caused slowly developing tension that reached its maximum after about 1 hr. This contraction was partially inhibited by pretreatment of the tissue with phentolamine (5 X 10(-6) M) or indomethacin (10(-5) M). The contraction induced by pCrTX was partially inhibited by nicardipine (10(-7) M) and markedly augmented by Bay k8644 (10(-6) M). In low-Na+ solution, the rate of rise of the pCrTX-induced contraction was significantly reduced. Removal of external Ca2+ inhibited the pCrTX-induced contraction by about 30%, while chlorpromazine, trifluoperazine, prenylamine and papaverine (10(-4) M) completely inhibited the contraction. pCrTX itself did not cause any contraction in saponin-skinned smooth muscle and had no effect on the Ca2+-induced contractile tension. It has been reported that pCrTX-induced contraction is attributable to the release of endogenous catecholamines and also to the increase in Ca2+ influx in smooth muscle (Azuma et al., 1986). The present results confirmed the previous suggestion and further suggested that a portion of the contraction is due to release of prostaglandin(s) and also to the direct effect on smooth muscle which is not dependent on Ca2+ influx.