Selenite and Ca2+ homeostasis in the rat lens: effect on Ca-ATPase and passive Ca2+ transport.
Calcium permeability was significantly increased in lenses from rats 36 h following a single injection of a cataractogenic dose of sodium selenite (30 nmol/g body weight) and this permeability returned to control values by 72 h post-injection (PI). The greater Ca2+ permeability could be partially reversed by incubating lenses in medium containing 2 mM dithiothreitol (DTT). Estimations of Ca-ATPase activity revealed the greatest level occurred in the epithelial layer and that the nucleus had no detectable activity. By 48 h PI both Ca(2+)-pump activity and the Ca(2+)-dependent ATP hydrolytic activity were less compared to controls in membrane preparations from rat lenses. Only the hydrolytic activity could be partially restored by treatment with 5 mM DTT. Both permeability and active Ca2+ transport were affected by selenite in a manner that would lead to increased Ca2+ accumulation in lenses from rats treated with selenite. It is suggested that the oxidative damage that accompanies in vivo exposure to selenite could affect Ca2+ homeostasis in the lens by directly altering permeability and Ca-ATPase.
Department of Biochemistry and Nutrition, Virginia Polytechnic Institute and State University, Blacksburg 24061-0308.
Z
Z
Wang
G E
GE
Bunce
J L
JL
Hess
D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002386:Cataract / Q000139:chemically induced; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D002463:Cell Membrane Permeability / Q000187:drug effects; D004229:Dithiothreitol / Q000494:pharmacology; D004848:Epithelium / Q000187:drug effects; D006706:Homeostasis; D007279:Injections, Subcutaneous; D007908:Lens, Crystalline / Q000187:drug effects* / Q000201:enzymology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012643:Selenium / Q000378:metabolism*; D018038:Sodium Selenite
D000252:Calcium-Transporting ATPases; D012643:Selenium; D018038:Sodium Selenite; D002118:Calcium; D004229:Dithiothreitol