Immunoreactivity of L–Kynurenine Aminotransferases in Human Cataractous Lenses

Abstract

Purpose: : This study is the first to investigate manifestation of L kynurenine aminotransferases (KAT I and II) immunoreactivity in the human lens and its changes due to cataract formation.

Methods: : Immunohistochemistry was conducted using polyclonal antibodies against KAT I and KAT II on sections of 6 anterior capsules from patients undergoing operative treatment of anterior subcapsular cataract and 22 cataractous lenses from eyes enucleated because of choroidal malignant melanoma. Cataractous lenses were grouped into four classifications: nuclear, mixed cortical and nuclear, and anterior capsular. For the control 4 clear lenses from eyes enucleated because of choroidal malignant melanoma were used. The spatial and temporal immunoreactivity patterns of both enzymes were then compared with PAS–stained sections.

Results: : Immunohistochemical analysis revealed presence of KAT I and KAT II in the extracellular structures of all studied types of cataract showing specific pattern of the stain. In fibrous metaplasia immunoreactivity was concentrated between epithelial cells underlying the anterior capsule. In cortical cataract the immunoreactivity was observed on cortical lens fibres. In nuclear cataract KAT II revealed stronger and diffused staining than KAT I. Additionally, both KAT showed more pronounced staining at the edge of small clefts. In normal lens KAT I and II immunoreactivity was not observed.

Conclusions: : Manifestation of L–kynurenine aminotransferases in extracellular matrix during human cataract formation suggests that products of l–kynurenine pathway might be involved in mechanisms of cataractogenesis.

Keywords: crystalline lens • cataract • enzymes/enzyme inhibitors