Helical strips of coronary arteries from normotensive and deoxycorticosterone acetate (DOCA) hypertensive rats were studied in vitro for their responsiveness to a variety of vasoactive agents. After application of passive force (50-400 mg), arteries developed spontaneous tonic contractions. These tonic contractions were not different between the two groups, and the contractions were not altered by inhibitors of neurogenic, prostaglandin, peptidergic, or purine activity. Coronary arteries from DOCA rats were more sensitive (lower effective dose, 50%) to the contractile effects of norepinephrine, serotonin, and potassium chloride relative to those from normotensive rats. Following contraction induced by serotonin, coronary arteries from DOCA rats relaxed less to isoproterenol and adenosine compared with those from control rats. Relaxation of arteries from DOCA rats in response to prostacyclin, nitroprusside, and acetylcholine did not differ from that in coronary arteries from normotensive rats. These observations demonstrate increased vascular sensitivity to constrictor agents and altered relaxation responses to adenosine and isoproterenol in the coronary vasculature of DOCA hypertensive rats.
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