Cyclic AMP and anionic currents in porcine ciliary epithelium

Introduction: To investigate whether in the ciliary epithelium of isolated porcine ciliary body cyclic 3 ' ,5 ' adenosine monophosphate (cAMP) activat es transmembrane anionic currents. Methods: Changes in membrane potential induced either by the adenylcyclase activator forskolin (10 muM; n = 4) or the stable membrane permeable cAMP a nalog 8-bromo-adenosine 3 ' ,5 ' -cyclic monophosphothioate (8-br-cAMP; 30 muM; n = 4) were measured with intracellular microelectrodes. The effect of the drugs were assessed in the absence or in the presence of the non-selec tive anionic channel/transporter inhibitor diisothiocyanatostilbene-2.2 ' d isulfonic acid (DIDS; 1 mM; n = 4). Results: Significant (p<0.001) membrane potential depolarization were induc ed by both forskolin (11 <plus/minus> 0.3 mV) or 8-br-cAMP (9.3 +/- 0.4mV). In the presence of DIDS, a significant (p<0.001) inhibition of the depolar ization evoked by forskolin (0.3 <plus/minus> 1.1 mV) and 8-bromo-cAMP (0.7 +/- 0.2 mV) was observed. Conclusions: In the ciliary epithelium of isolated porcine ciliary body cAM P induces membrane potential depolarization through a process that could in volve anionic channels.