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T A Karnezis, B J Tripathi, G Dawson, M B Murphy, R C Tripathi; Effects of dopamine receptor activation on the level of cyclic AMP in the trabecular meshwork.. Invest. Ophthalmol. Vis. Sci. 1989;30(6):1090-1094.
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We examined the effects of dopamine and of a selective DA1 agonist, fenoldopam, on the levels of cyclic AMP in the trabecular meshwork, freshly excised from porcine and canine eyes. As measured by radioimmunoassay, fenoldopam at a concentration of 10(-5) M caused a 4-fold increase in the cyclic AMP content, from a basal level of 24.4 +/- 1.9 to 101.8 +/- 6.3 pmol/mg protein, of the trabecular meshwork samples from porcine eyes. In tissue samples from canine eyes, fenoldopam at a concentration of 10(-4) M increased the endogenous cyclic AMP level from a basal value of 26.0 +/- 4.6 to 64.2 +/- 5.7 pmol/mg protein. Dopamine, although less potent, produced a similar response. Preincubation with a DA1 receptor antagonist, SCH 23390, inhibited the increase in cyclic AMP levels by 90%. Such inhibition did not occur with the alpha- and beta-receptor antagonists phenoxybenzamine and propranolol, respectively. This investigation demonstrates that adenylate cyclase-coupled DA1 receptors are present in porcine and canine trabecular meshwork tissue.
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