OBJECTIVE: Crassostrea gigas oyster extract has been reported to have antioxidant, antihypertensive and lipid-lowering properties that may be useful for treating cardiovascular diseases. This study aimed to evaluate the effect of C. gigas oyster extract on cardiovascular function in tissues from healthy rats. METHODS: Single-cell microelectrode and isolated thoracic aortic organ bath studies were performed on tissues from 8-week-old healthy Wistar rats, using varying concentrations of C. gigas oyster extract. To elucidate a mechanism of action for the oyster’s vasoactive properties, concentration response curves were carried out in the presence of a calcium channel inhibitior(verapamil), a nitric oxide synthase inhibitor(N G-nitro-L-arginine methyl ester), a potassium channel inhibitor(4-aminopyridine), in addition to the α-adrenoceptor inhibitor prazosin. RESULTS: Oyster solution at 7 500 mg/m L inhibited noradrenaline-induced contraction in isolated aortic rings. Cardiac electrophysiology results showed that neither concentration of oyster solution was able to significantly reduce action potential duration at all phases of repolarisation in left ventricular papillary muscles from healthy animals. CONCLUSION: When administered to healthy vascular tissue, C. gigas oyster extract inhibits contraction induced by noradrenaline. This effect is likely to be mediated through α-adrenoceptor inhibition, and to a lesser extent, calcium modulating activity. OBJECTIVE: Crassostrea gigas oyster extract has been reported to have antioxidant, antihypertensive and lipid-lowering properties that may be useful for treating cardiovascular diseases. This study aimed to evaluate the effect of C. gigas oyster extract on cardiovascular function in tissues from healthy rats. METHODS: Single-cell microelectrode and isolated thoracic aortic organ tubular studies were performed on tissues from 8-week-old healthy Wistar rats, using varying concentrations of C. gigas oyster extract. To elucidate a mechanism of action for the oyster’s vasoactive properties, concentration response curves were carried out in the presence of a calcium channel inhibitor (verapamil), a nitric oxide synthase inhibitor (N G-nitro-L-arginine methyl ester), a potassium channel inhibitor (4-aminopyridine) -adrenoceptor inhibitor prazosin. RESULTS: Oyster solution at 7 500 mg / m L inhibited noradrenaline-induced contraction in isolated aortic rings. Cardiac electrophysiology iology results showed that neither concentration of oyster solution was able to significantly reduce action potential duration at all phases of repolarisation in left ventricular papillary muscles from healthy animals. CONCLUSION: When administered to healthy vascular tissue, C. gigas oyster extract inhibits contraction induced by noradrenaline This effect is likely to be mediated mediated through α-adrenoceptor inhibition, and to a lesser extent, calcium modulating activity.