Role of anions in nitric oxide-induced short-circuit current increase in isolated porcine ciliary processes.
OBJECTIVE
To investigate how nitric oxide (NO) modulates short-circuit current (Isc) in isolated porcine ciliary processes.


METHODS
Isc changes (Ussing-type chamber) induced either by the NO donors SNP or SIN-1, or by the cGMP analogue 8-pCPT-cGMP were assessed. The effect of inhibitors of guanylate cyclase (10 microM ODQ, 100 microM LY83583), protein kinase G (30 microM Rp-8-pCPT-cGMP, 3 microM KT 5823), protein kinase A (1 microM KT 5720), or protein kinase C (1 microM Go6983) on SNP- or 8-pCPT-cGMP-induced Isc changes were investigated. The effect of inhibitors of anion channel (100 microM niflumic acid, 1 mM DIDS, and 1 mM 9-AC), K+-channel (10 mM TEA, 10 mM BaCl2), Na+-channel blockers (1 mM amiloride), Na+-K+-2Cl- cotransporter inhibitor (0.5 mM bumetanide), or carbonic anhydrase inhibitor (1 mM acetazolamide) was studied. In Cl(-)- or HCO3(-)-free Krebs-Ringer solution, the effect of SNP- or 8-pCPT-cGMP-induced Isc changes was accessed.


RESULTS
SNP, SIN-1, or 8-pCPT-cGMP increased Isc with a change in the potential difference that became more negative toward the nonpigmented epithelium (aqueous) side. The Isc increase induced by SNP or SIN-1, but not by 8-pCPT-cGMP, was prevented by ODQ and LY83583. SNP- and 8-pCPT-cGMP-induced Isc increases were prevented by Rp-8-pCPT-cGMP or KT5823 (but not by KT5720 or Go6983), or by niflumic acid, DIDS, 9-AC, or acetazolamide (but not by TEA, BaCl2, amiloride, or bumetanide). The effect of SNP and 8-pCPT-cGMP was abolished in Cl(-)- and reduced in HCO3(-)-free solutions.


CONCLUSIONS
NO activates a guanylate cyclase-cGMP-protein kinase G pathway that appears to stimulate stroma-to-aqueous anionic transport, possibly Cl-, in porcine ciliary epithelium.
Laboratory of Ocular Pharmacology and Physiology, University Eye Clinic Basel, Basel, Switzerland.
Renyi
R
Wu
Ke
K
Yao
Josef
J
Flammer
Ivan O
IO
Haefliger
D000818:Animals; D027321:Anion Transport Proteins / Q000378:metabolism; D000838:Anions / Q000378:metabolism*; D001082:Aqueous Humor / Q000378:metabolism; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology; D018118:Chloride Channels / Q000037:antagonists & inhibitors; D002924:Ciliary Body / Q000502:physiology*; D003319:Corneal Stroma / Q000378:metabolism; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D004553:Electric Conductivity; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D007474:Ion Exchange; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D013552:Swine; D013873:Thionucleotides / Q000494:pharmacology
D027321:Anion Transport Proteins; D000838:Anions; D002257:Carbonic Anhydrase Inhibitors; D018118:Chloride Channels; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D047428:Protein Kinase Inhibitors; D013873:Thionucleotides; D009599:Nitroprusside; D009569:Nitric Oxide; C055656:8-((4-chlorophenyl)thio)cyclic-3',5'-GMP; C002385:linsidomine; D008981:Molsidomine; D006162:Guanylate Cyclase; D006152:Cyclic GMP