Trace element distribution in human eye

Selenium concentrations in serum, lens and aqueous humour of patients with senile cataract

Selenium (Sc) is a trace element which incorporates into the selenoenzyme glutathion peroxidase. Cataractogenesis may be caused either by the excess or deficiency of this trace element. More recently, its potential of becoming a possible environmental pollutant has been emphasized. In an attempt to reveal the relationship of this element with cataractogenesis, we detected its level in 48 serum, 36 lens and 9 aqueous humour samples of 48 patients with senile cataract, comparing the results with appropriate controls. Selenium levels (mean +/- SD) of cataractous patients were found to be 0.28 +/- 0.04 microgram/ml (CI: 0.27 to 0.29 microgram/ml) in sera (controls: 0.32 +/- 0.04 microgram/ml; CI: 0.30 to 0.34 microgram/ml, p < 0.0001), 5.43 +/- 3.07 microgram/g dry weight (CI: 4.43 to 6.43 microgram/g dry weight) in lens (controls: 4.43 +/-2.53 microgram/g dry weight; CI: 2.78 to 6.08 microgram/g dry weight; p=0.374) and 0.19 +/- 0.06 microgram/ml (CI:0.15 to 0.23 microgram/ml) in aqueous humour samples (controls: 0.31 +/-0.12 microgram/ml; CI: 0.24 to 0.38 microgram/ml, p = 0.02). When patient subgroups were analyzed, serum Se levels were found to be 0.28 +/- 0.05 microgram/ml (CI: 0.26 to 0.30 microgram/ml in the nuclear cataract and 0.28 +/- 0.02 microgram/ml (CI: 0.27 to 0.30 microgram/ml) in the cortical cataract. Lens Se levels, on the other hand, were detected as 5.91 +/- 3.56 microgram/g dry weight (CI:4.49 to 7.33 microgram/g dry weight) in the nuclear cataract and 4.47 +/- 1.40 microgram/g dry weight (CI: 3.68 to 5.26 microgram/g dry weight) in the cortical cataract. It is anticipated that decreased Se in aqueous humour and sera of patients with senile cataract may reflect defective antioxidative defense systems which may lead to the formation of cataract.

Review of selenite cataract

Recent advances in understanding the mechanism of selenite cataract have resulted from locating the cleavage sites on proteolyzed beta-crystallins from the cataract, mimicking the insolubilization of crystallins found in the cataract in an in vitro system, studying cataract produced in lenses cultured in selenite, and permanently or temporarily reducing the rate formation of selenite cataract by use of various inhibitors. The present review discusses the selenite cataract as a useful model for understanding the role calcium-induced proteolysis in cataract formation.