Carbonic anhydrase: General perspective and advances in glaucoma research

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Abstract
The chemistry and physiology of carbonic anhydrase are reviewed in relation to pharmacological progress in the development of sulfonamide inhibitors. The major organ systems are briefly dicussed. From the medical point of view, the major thrust is now for the treatment of glaucoma. The physiology of aqueous humor formation with respect to ion transport is discussed, and it is shown that a key event is the catalytic formation of HCO3− from CO2 and OH−. The newly formed HCO3− is linked to NA+ and fluid movement to produce aqueous humor. Inhibition of HCO3− sunthesis sulfonamides reduces aqueous formation and lowers pressure in normals and in glucoma.Four sulfonamides have been used sytemically, the chief being acetazolamide. None of these works topically; they do not reach the ciliary process in adequate concetrations. New programs have begun, searching for sulfonamides of different properties that cross the cornea in effective concetrations to inhibit carbonic anhydrase in the ciliary porcess. The key to the problems seems to be to search for a balance between water and lipid solubility, maintaining high activity against the enzyme. This has been achieved, and new structures described from this and other laboratories lower pressure in the rabbit nearly as well as systemic sulfonamides.Corneal permeabilities to test compounds (in vitro) in rabbit and man are similar, but accession to the auqeous (in vivo) is less in man. This may make the goal difficult, and the reasons for this difference are being explored.