Susceptibility of Weakly Ouabain-Sensitive Na, K-ATPase Isoform in Ischemic and Reperfused Rat Retinas
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JUNKO KUBOKI, SEI-ICHI ISHIGURO and MAKOTO TAMAI
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Department of Ophthalmology, Tohoku University School of Medicine, Sendai 980-8574
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 (a) and highly ouabain-sensitive (a[+]) isoform activities separately by ATP hydrolysis. Total ouabain-sensitive Na, K-ATPase activity, a and a(+) 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 a and a(+) isoforms were 47% and 72%, respectively. The ratios of the a and a(+) isoform activities (a/a[+]) 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.
Key words---
Na, K-ATPase; a isoform; ischemia; oxidative stress
© 1999 Tohoku University Medical Press
Tohoku J. Exp. Med., 1999, 187, 353-361
Address for reprints:
Junko Kuboki, M. D., Department of Ophthalmology, Tohoku University School of Medicine, 1-1 Seiryomachi, Aoba-ku, Sendai 980-8574, Japan.
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