Inhibition of rat brain Na⁺-K⁺-ATPase by triterpene glycosides from holothurians

I. A. Gorshkova, B. A. Gorshkov and V. A. Stonik. Inhibition of rat brain Na⁺-K⁺-ATPase by triterpene glycosides from holothurians. Toxicon 27, 927-936, 1989.-The effect of triterpene glycosides from holothurians on Na⁺-K⁺-ATPase of rat brain was investigated. The marine glycosides are irreversible inhibitors of the enzyme with an average I₅₀ value of 10^-4 M. ATP had a low protective effect against inhibition. The inhibitory effect was increased by preincubation with MgCl₂. There was alteration of the activation curve of Na⁺-K⁺-ATPase by NaCl and KCl in the presence of glycosides. Triterpene glycosides inhibited the K⁺-phosphatase activity, but to a smaller degree than the ATPase activity. Na⁺-K⁺-ATPase of pig kidney was less sensitive to the marine triterpene glycosides than the brain enzyme. The marine glycosides did not alter the specific binding of [³H]-ouabain to the Na⁺-K⁺-ATPase.