TOPOGRAPHICAL DISTRIBUTION OF LACTATE-DEHYDROGENASE ACTIVITY IN HUMANCLEAR EYE LENSES AND IN LENSES WITH DIFFERENT TYPES OF SENILE CATARACT - A HISTOCHEMICAL INVESTIGATION

Background: Homogenates of human clear lenses show an age-dependent re duction of enzyme activities. Topographical patterns of enzymes in cle ar and cataractous lenses can be visualized by histochemistry. Materia l and methods: Human lenses were characterized by slit-lamp investigat ions as bearing different types of senile cataracts. Subsequently, len ses were removed by intracapsular extraction. Clear human lenses serve d as controls, Bovine lenses served to standardize freeze-cutting and incubation for lactate dehydrogenase histochemistry. Results: Bovine l enses show a sharp demarcation between the enzyme reaction of cortical fibers bearing cell nuclei and the non-reacting deeper fibers not exh ibiting cell nuclei. Clear human lenses, lenses with deep supranuclear cortical cataracts, and lenses with nuclear cataracts exhibit the sam e borderline. However, in lenses with a subcapsular cortical cataract only the epithelium and a very thin layer of the most superficially lo cated fibers show positive enzyme reactions. Conclusion: In growing cl ear human and bovine lenses, independent of age, the more peripherally located cortical fibers bearing cell nuclei exhibit strong enzyme-his tochemical reactions. More centrally located lens areas lacking cell n uclei increase in volume in an age-dependent manner. These lens region s do not exhibit enzyme activities detectable by our histochemical tec hnique. Therefore the lens areas free of histochemical reaction produc t become larger with increasing age, whereas the peripherally located lens fibers apparently do not change their enzyme activities with age. Thus, homogenates of total lenses show age-dependent reductions of en zyme activities, although enzyme activities remain at a physiological level in cortical lens fibers with recognizable cell nuclei. In lenses with immature supranuclear cortical and (particularly) in lenses with black nuclear cataracts, cortical fibers still can exhibit high enzym e activities. Unexpectedly, also ruptured and broken fibers in immatur e deep supranuclear cortical cataracts show strong enzyme activities. In contrast, in lenses with (incipient) subcapsular cortical cataracts only the most superficially located lens fibers exhibit some enzyme a ctivity.