To investigate and compare the effects of topical carbonic anhydrase inhibitors on the production and expression of nitric oxide in cultured human trabecular meshwork cells (HTMC).

Primarily cultured HTMC were exposed to 0, 10, and 100 µM dorzolamide and brinzolamide using serum-deprived media for 3 days. Production of nitric oxide was assessed with Griess assay. Expressions of eNOS mRNA were assessed with RT-PCR.

Both dorzolamide and brinzolamide increased the production of nitric oxide eNOS activity ( p < 0.05). Dorzolamide had a more potent effect than brinzolamide on the production of nitric oxide and the expression of eNOS mRNA.

Topical carbonic anhydrase inhibitors increased the production of nitric oxide, which was accompanied by increased eNOS activity. Dorzolamide had a more potent effect than brinzolamide on the production of nitric oxide and expression of eNOS mRNA in HTMC. The increased production of nitric oxide by topical carbonic anhydrase inhibitors involves mechanisms other than carbonic anhydrase inhibition.