Vascular reactivity of the coronary artery in rainbow trout (Oncorhynchus mykiss).

Vascular reactivity of the large coronary artery of a lower vertebrate was investigated for the first time in this study. The responses of vascular rings to various pharmacological agents were measured using isometric force transducers. Coronary arteries from rainbow trout, Oncorhynchus mykiss, contracted with acetylcholine and predominantly relaxed with isoproterenol, epinephrine, norepinephrine, and serotonin. Atenolol blocked the adrenergic relaxation, suggesting a predominance of beta 1-adrenoceptors. Nitroglycerin and sodium nitroprusside relaxed vascular rings. Responses to histamine and bradykinin were absent in this tissue. Adenosine, ADP, and ATP caused contractions that could be blocked by theophylline. The difference in vascular reactivity between that typically found in mammalian coronary arteries and that reported here for rainbow trout are discussed.