Topographical distribution of lactate dehydrogenase activity in human clear eye lenses and in lenses with different types of senile cataract: a histochemical investigation

Abstract

• Background: Homogenates of human clear lenses show an age-dependent reduction of enzyme activities. Topographical patterns of enzymes in clear and cataractous lenses can be visualized by histochemistry. • Material and methods: Human lenses were characterized by slit-lamp investigations as bearing different types of senile cataracts. Subsequently, lenses were removed by intracapsular extraction. Clear human lenses served as controls. Bovine lenses served to standardize freeze-cutting and incubation for lactate dehydrogenase histochemistry. • Results: Bovine lenses show a sharp demarcation between the enzyme reaction of cortical fibers bearing cell nuclei and the non-reacting deeper fibers not exhibiting cell nuclei. Clear human lenses, lenses with deep supranuclear cortical cataracts, and lenses with nuclear cataracts exhibit the same borderline. However, in lenses with a subcapsular cortical cataract only the epithelium and a very thin layer of the most superficially located fibers show positive enzyme reactions. • Conclusion: In growing clear human and bovine lenses, independent of age, the more peripherally located cortical fibers bearing cell nuclei exhibit strong enzyme-histochemical reactions. More centrally located lens areas lacking cell nuclei increase in volume in an age-dependent manner. These lens regions do not exhibit enzyme activities detectable by our histochemical technique. Therefore the lens areas free of histochemical reaction product 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 enzyme 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 enzyme activities. Unexpectedly, also ruptured and broken fibers in immature 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 activity.