Ultrathin-layer microelectrophoretic determination of lactate dehydrogenase isoenzymes in corneal and conjunctival epithelium of the cow.

In order to evaluate the impact of tissue oxygenation on the distribution pattern of lactate dehydrogenase isoenzymes, activities of the isoenzymes were measured in microdissected samples of bovine tissue. A highly sensitive ultrathin-layer electrophoretic technique was used to determine the distribution pattern of lactate dehydrogenase isoenzymes in basal, intermediate and superficial layers of the epithelium of central and peripheral cornea and in the epithelium of the bulbar conjunctiva. Measurements revealed almost homogeneous intraepithelial distribution patterns of lactate dehydrogenase isoenzymes in both tissues. In the cornea the lactate dehydrogenase isoenzymes 4 and 5, which are regarded to be specialized for anaerobic glucose metabolism, were found to predominate. In the well-oxygenated conjunctival epithelium most of the activity could be ascribed to the lactate dehydrogenase isoenzyme 3. In contrast to the isoenzymatic activities, total activity of lactate dehydrogenase was inhomogeneously distributed; maximum activities were found in the basal layer of corneal epithelium and in the intermediate layer of conjunctival epithelium. The results indicate that oxygen supply is relevant rather for the intraepithelial distribution of total enzyme activity than for the expression of lactate dehydrogenase isoenzymes.