title: Alpha-adrenoceptor antagonism by Crassostrea gigas oyster extract inhibits noradrenaline-induced vascular contraction in Wistar rats.
abstract: 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/mL 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: School of Medical and Applied Sciences, CQUniversity Australia, Rockhampton, Queensland 4702, Australia.
authors.forename: Kylie
authors.initials: K
authors.lastname: Connolly
authors.affiliation: School of Medical and Applied Sciences, CQUniversity Australia, Rockhampton, Queensland 4702, Australia.
authors.forename: Douglas
authors.initials: D
authors.lastname: Jackson
authors.affiliation: School of Medical and Applied Sciences, CQUniversity Australia, Rockhampton, Queensland 4702, Australia.
authors.forename: Candice
authors.initials: C
authors.lastname: Pullen
authors.affiliation: School of Medical and Applied Sciences, CQUniversity Australia, Rockhampton, Queensland 4702, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Fenning
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D049896:Crassostrea; D006321:Heart / Q000187:drug effects / Q000502:physiology; D008297:Male; D009638:Norepinephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D000317:Adrenergic alpha-Antagonists; D002118:Calcium; D009638:Norepinephrine