TY - JOUR
T1 - Inhibition of Adenylate Cyclase in Bovine Ciliary Process and Rabbit Iris Ciliary Body to Alpha2-Adrenergic Agonists
AU - Jin, Ying
AU - Elko, E. E.
AU - Tran, Tung
AU - Yorio, Thomas
PY - 1989
Y1 - 1989
N2 - Alpha2-adrenergic inhibition of adenylate cyclase in bovine ciliary processes and rabbit iris ciliary body (ICB) was studied. With bovine ciliary process membrane, it was found that cAMP production in the presence of 1 μM isoproterenol was increased with increasing NaCl concentrations from 0 to 200 mM. Clonidine, an α2-adrenergic agonist, produced a NaCl concentration- dependent inhibition of cAMP production in the presence of isoproterenol with a maximum inhibition at 200 mM NaCl (P<0.05). NaCl concentrations had no effect on basal adenylate cyclase activities and activity in the presence of clonidine alone. The α2-adrenergic agonists, lofexidine, clonidine and p-amino-clonidine were tested for their ability to inhibit isoproterenol-stimulated adenylate cyclase in bovine ciliary process membrane in the presence of 200 mM NaCl. Their dose-response curves showed that they had similar IC50's but the maximum inhibition differed among these agonists. Clonidine was found to be a partial agonists producing 55% of the inhibition obtained with lofexidine. The specificity of inhibition of isoproterenol-stimulated adenylate cyclase by α2-agonists and blockade by pertussis toxin was examined by adenine labelling in rabbit ICB. The results demonstrate that α2-adrenergic receptors exert specific inhibitory effects on adenylate cyclase activity in rabbit ICB, which are mediated by an inhibitory guanine nucleotide regulatory protein, Gi.
AB - Alpha2-adrenergic inhibition of adenylate cyclase in bovine ciliary processes and rabbit iris ciliary body (ICB) was studied. With bovine ciliary process membrane, it was found that cAMP production in the presence of 1 μM isoproterenol was increased with increasing NaCl concentrations from 0 to 200 mM. Clonidine, an α2-adrenergic agonist, produced a NaCl concentration- dependent inhibition of cAMP production in the presence of isoproterenol with a maximum inhibition at 200 mM NaCl (P<0.05). NaCl concentrations had no effect on basal adenylate cyclase activities and activity in the presence of clonidine alone. The α2-adrenergic agonists, lofexidine, clonidine and p-amino-clonidine were tested for their ability to inhibit isoproterenol-stimulated adenylate cyclase in bovine ciliary process membrane in the presence of 200 mM NaCl. Their dose-response curves showed that they had similar IC50's but the maximum inhibition differed among these agonists. Clonidine was found to be a partial agonists producing 55% of the inhibition obtained with lofexidine. The specificity of inhibition of isoproterenol-stimulated adenylate cyclase by α2-agonists and blockade by pertussis toxin was examined by adenine labelling in rabbit ICB. The results demonstrate that α2-adrenergic receptors exert specific inhibitory effects on adenylate cyclase activity in rabbit ICB, which are mediated by an inhibitory guanine nucleotide regulatory protein, Gi.
UR - http://www.scopus.com/inward/record.url?scp=0024802626&partnerID=8YFLogxK
U2 - 10.1089/jop.1989.5.189
DO - 10.1089/jop.1989.5.189
M3 - Article
C2 - 2576279
AN - SCOPUS:0024802626
SN - 1080-7683
VL - 5
SP - 189
EP - 197
JO - Journal of Ocular Pharmacology and Therapeutics
JF - Journal of Ocular Pharmacology and Therapeutics
IS - 3
ER -