Effects of selenium on ion homeostasis and transparency in cultured lenses

Selenium toxicity was investigated in cultured rabbit lenses to provide further information about the role of Ca++ in Se cataract. At a dose of 0.1 mM for 20 hr, Se induces a 10% change in Na levels within 6 hr, a 30% increase after 20 hr, and a three-fold increase within 48 hr of subsequent culture after removal of Se. In contrast, Ca++ levels remained normal throughout the first 24 hr. Only a small, 25% decline in GSH was noted. Not until lenses begin to swell and become noticeably opaque and turbid were Ca++ levels found to be elevated. Thus, at 72 hr, 48 hr following the removal of selenium, Ca++ had increased to a concentration of 0.7 mM. Ca++ accumulation appears to be a consequence of osmotic stress rather than pump inhibition while Na accumulation is a direct consequence of Se-inhibited Na pump.