THE EFFECT OF X-IRRADIATION ON NA-K ATPASE AND CATION DISTRIBUTION IN RABBIT LENS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 22  (2) , 180-185
Abstract
The Na-K ATPase activity of rabbit lens was measured at various times after exposure to a single dose of 2000 rads of X-ray and was compared with that in contralateral control eyes. A decrease in enzyme activity in both whole lens and in isolated capsule-epithelium was first observed 3-4 wk after irradiation, and became increasingly marked 7.5 wk after X-ray. These findings are consistent with earlier observations that active transport of cations is reduced in these lenses; the view that loss of membrane ATPase is responsible for the impairment of the cation pump in X-irradiated lenses is supported. Despite a significant loss of the enzyme X-irradiated lenses were able to maintain near normal levels of total cations (Na+ + K+), accounting for their normal hydration. The results of the changes in lens Na+ and K+ levels revealed that, between 4 and 7.5 wk after X-ray, the gain in Na+ was compensated by an equivalent loss of K+. A breakdown of this relationship of 1:1 exchange of Na+ for K+ is accompanied by a disproportionate increase in Na+ and water.