Effects of dopamine receptor activation on the level of cyclic AMP in the trabecular meshwork.
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.
Karnezis
T A
TA
Department of Ophthalmology and Visual Science, University of Chicago, Illinois.
Tripathi
B J
BJ
Dawson
G
G
Murphy
M B
MB
Tripathi
R C
RC
D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D000242:Cyclic AMP / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004285:Dogs; D018492:Dopamine Antagonists; D018818:Fenoldopam; D011433:Propranolol / Q000494:pharmacology; D011954:Receptors, Dopamine / Q000502:physiology*; D013552:Swine; D014129:Trabecular Meshwork / Q000378:metabolism*
D001552:Benzazepines; D018492:Dopamine Antagonists; D011954:Receptors, Dopamine; D011433:Propranolol; D000242:Cyclic AMP; D018818:Fenoldopam