Endothelins inhibit cyclic AMP production in rabbit and human ciliary processes.

The effects of endothelins on cyclic AMP production have been studied in rabbit and human ciliary processes. Endothelins inhibit basal, isoproterenol-, and VIP-stimulated cyclic AMP production in rabbit ciliary processes and forskolin-stimulated cyclic AMP production in rabbit and human ciliary processes. EC50s for inhibition of forskolin-stimulated cyclic AMP production using rabbit tissue were similar: ET-1, 70 nM; ET-2, 40 nM; ET-3, 70 nM; maximum inhibition was about 76% for each ligand. These data are consistent with the presence of an ETB receptor. Endothelin-like immunoreactivity in rabbit aqueous humor was measured to be 226 pg/ml.