M. Sharir et al., NOVEL TOPICAL THIADIAZOLES AND BENZOTHIAZOLES AS PHARMACOLOGICAL PROBES OF CORNEAL ENDOTHELIAL FUNCTION, Journal of ocular pharmacology, 9(4), 1993, pp. 333-340
Corneal transparency is maintained by an active transport system, loca
ted at the endothelial cell membranes. This bicarbonate-dependent pump
counteracts the tendency of the corneal stroma to absorb water, swell
and become opaque. Carbonic anhydrase inhibitors (CAI) are capable of
attenuating the bicarbonate efflux, therefore causing thickening of t
he cornea. Eight novel sulfonamides were evaluated as potential probes
for assessing the corneal endothelial functional reserves. Five of th
e six thiadiazoles and both benzothiazoles have demonstrated carbonic
anhydrase inhibitory properties in vitro. Of the eight compounds teste
d, 2-ethyladipoyl-1,3,4-3,4-thiadiazole-5-sulfonamide (compounds III),
2-epoxy-1,3,4-thiadiazole-5-sulfonamide (compound V), and -acetamido-
1,3,4-thiadiazole-5-N-methylsulfonamide (compound VI) have induced rev
ersible corneal thickening. Although statistically significant (p < 0.
05), the magnitude of the pachymetric effect did not exceed 6-10% of t
he total corneal thickness, probably because carbonic anhydrase (CA) i
s only one component of the active pump complex. The fact that a non-C
AI (compound VI) was capable of inducing a reversible corneal thickeni
ng may suggest that other mechanisms are involved. Further studies wil
l. be conducted to identify a pharmacological agent capable of reversi
bly inhibiting the endothelial function in normal and diseased corneas
, with a higher magnitude of effect.