Susceptibility of weakly ouabain-sensitive Na, K-ATPase isoform in ischemic and reperfused rat retinas.
It is possible that Na, K-ATPase may play some roles in ischemic damage of nervous tissue. To determine whether Na, K-ATPase is affected in ischemic and reperfused retina, we measured enzyme activities. Retinal ischemia was induced by clamping the optic nerve of female adult Sprague-Dawley (SD) rats for 90 minutes. At 0.5, 2 and 24 hours after reperfusion, rat eyes were enucleated, and the retinas were removed. In addition to unseparated, total ouabain-sensitive Na, K-ATPase activity, we measured weakly ouabain-sensitive (alpha) and highly ouabain-sensitive (alpha[+]) isoform activities separately by ATP hydrolysis. Total ouabain-sensitive Na, K-ATPase activity, alpha and alpha(+) isoform activities showed no significant difference from sham-operated contralateral eyes at 0.5 and 2 hours of reperfusion. After 24 hours of reperfusion, total ouabain-sensitive Na, K-ATPase activity decreased to 63% of the control. The activities of alpha and alpha(+) isoforms were 47% and 72%, respectively. The ratios of the alpha and alpha(+) isoform activities (alpha/alpha[+]) significantly decreased at 2 and 24 hours of reperfusion. Activity in a isoform decreased markedly in reperfused rat retinas. This response may be beneficial for reducting the oxidative stress in reperfused retinas.
Kuboki
J
J
Department of Ophthalmology, Tohoku University School of Medicine, Sendai, Japan.
Ishiguro
S
S
Tamai
M
M
D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D007527:Isoenzymes / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000201:enzymology*; D012160:Retina / Q000201:enzymology* / Q000473:pathology*; D012161:Retinal Artery / Q000473:pathology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*
D004791:Enzyme Inhibitors; D007527:Isoenzymes; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase