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  • Title: Cerebrovascular smooth muscle culture. II. Characterization of adrenergic receptors linked to adenylate cyclase.
    Author: Wroblewska B, Spatz M, Merkel N, Bembry J.
    Journal: Life Sci; 1984 Feb 20; 34(8):783-91. PubMed ID: 6142395.
    Abstract:
    Cultured and propagated smooth muscle cells contain adenylate cyclase (AC) responsive to catecholamines and their analogues. Isoproterenol and zinterol were the most effective stimulants of AC activity with EC50 = 8.5 X 10(-8)M. They were followed by epinephrine, phenylephrine and norepinephrine (EC50 = 7.5 X 10(-7)M, 6.5 X 10(-6)M and 4 X 10(-6)M, respectively). When the selective antagonists for beta 1 and beta 2 receptors (beta 1-type practolol and atenolol, beta 1/beta 2-type propranolol and beta 2-type butoxamine) were tested against isoproterenol, epinephrine and norepinephrine stimulation of AC activity, the beta 1 in contrast to beta 2 antagonists were found ineffective. The alpha-blockers (phentolamine alpha 1/alpha 2-type antagonists) and yohimbine (alpha 2-type antagonist) alone or in the presence of propranolol did not significantly inhibit the catecholamine-induced enhancement of cAMP formation. On the other hand, prazosine (alpha 1-type antagonist) blocked the stimulatory effect of epinephrine and norepinephrine on AC system. Similarly, the alpha 2-agonist, clonidine, did not affect the catecholamines' stimulated AC activity while alpha 1 agonist, phenylephrine, induced an additive enhancement of norepinephrine production of cAMP. The findings of beta-2- and alpha-1-type adrenergic receptors in the cultured cerebrovascular smooth muscle provide additional support for the implicated involvement of adrenergic innervation in the regulation of cerebral blood flow and/or systemic blood pressure.
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