The microchemical detection of carbonic anhydrase in corneal epithelia

Carbonic anhydrase (CA) activity has been detected and quantified in the corneal epithelia of various mammalian species using a microchemical assay. The highest levels were found in the rabbit, followed by man, dog, sheep, and cat. Enzyme levels in the rabbit epithelium were approximately one-third the amount found in the endothelium, perhaps explaining earlier failures to find CA in the epithelium. Selective inactivation of CA-II in tissue homogenates with bromopyruvic acid allowed determination of CA-I/CA-II ratios. The ratios in corneal epithelia from two species (rabbit and dog) approximated that in the erythrocyte. Although CA levels in the epithelium are low they are perhaps functional in the transfer of CO2 across the cornea.