Calcium modulatory properties of O,O-diphenyl O-N-cyclooctyl phosphoramidate [corrected] isolated from Ptychodiscus brevis in rat atria and smooth muscle.
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1997-07-01
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Calcium modulatory activity of a marine toxin has been studied employing in vitro preparations. The toxin induced contracture in rat diaphragm was not modified by denervation, d-tubocurarine and tetrodotoxin (TTX). In contrast, varying concentrations of calcium, EGTA and ryanodine inhibited the contracture significantly. The toxin produced a series of repeating contractions in vas deferens. Experiments with TTX, adrenoceptor blockers and other agents exclude a release of neuromediators or direct stimulation of post synaptic receptors to account for the rhythmic effect in vas deferens. The dependence of rhythmicity on external Ca2+ concentration and inhibiting effect of Mn2+, ryanodine and nifedipine indicate a direct activation of voltage-sensitive calcium channel. The toxin also evoked a similar pattern of response in paced atria mediated through Ca2+ influx.
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Mazumder PK, Gupta AK, Kumar D, Dube SN. Calcium modulatory properties of O,O-diphenyl O-N-cyclooctyl phosphoramidate [corrected] isolated from Ptychodiscus brevis in rat atria and smooth muscle. Indian Journal of Physiology and Pharmacology. 1997 Jul; 41(3): 257-62