title: Alpha 2-adrenoceptor stimulation and cellular cAMP levels in microdissected rat glomeruli.
abstract: A functional role for the numerically predominant glomerular alpha 2-adrenoceptors is unknown. In other tissues, activation of alpha 2-adrenoceptors inhibits adenylate cyclase activity. We therefore examined the effect of alpha 2-adrenoceptor stimulation with (-)-epinephrine (E) on the cellular cAMP concentration in glomeruli isolated by microdissection. Parathyroid hormone (1-34 PTH), prostaglandin E2 (PGE2), histamine, serotonin, or adenosine, in the presence of 3-isobutyl-1-methylxanthine (phosphodiesterase inhibitor) and propranolol, was used to activate adenylate cyclase in single intact rat glomeruli. alpha 2-Adrenoceptors were activated with varying concentrations of E (37 degrees C, 2 min). In the presence of PTH-stimulated cAMP production, alpha 2-adrenoceptor activation with E (5 X 10(-7) to 5 X 10(-6) M) suppressed cellular cAMP levels in a dose-dependent fashion with the maximum at 30%. This suppression by E was inhibited by 5 X 10(-6) M yohimbine but not by 5 X 10(-6) M prazosin, confirming alpha 2-adrenoceptor mediation of this effect of E. Consistent with the above findings, the specific alpha 2-adrenoceptor agonist BHT933 inhibited PTH-stimulated cAMP accumulation. E also inhibited cAMP accumulation stimulated by serotonin. However, E did not suppress the PGE2-, histamine-, or adenosine-stimulated increase in cellular cAMP in the glomerulus. Activation of alpha 2-adrenoceptors inhibits cAMP formation stimulated by PTH or serotonin but not by PGE2, histamine, or adenosine in the rat glomerulus. Thus, the ability of alpha 2-adrenoceptors to inhibit adenylate cyclase appears to be hormone and probably function specific.
mesh_terms: D000241:Adenosine / Q000494:pharmacology; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D015232:Dinoprostone; D004210:Dissection / Q000379:methods; D004837:Epinephrine / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D007678:Kidney Glomerulus / Q000166:cytology / Q000378:metabolism*; D008297:Male; D010281:Parathyroid Hormone / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D011458:Prostaglandins E / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology; D013268:Stimulation, Chemical; D019379:Teriparatide
chemical_list: D001381:Azepines; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D011458:Prostaglandins E; D011942:Receptors, Adrenergic, alpha; D019379:Teriparatide; D012701:Serotonin; D006632:Histamine; C015603:azepexole; D000242:Cyclic AMP; D000241:Adenosine; D015232:Dinoprostone; D004837:Epinephrine