Effect of the pyridoindole antioxidant stobadine on sodium handling of renal Na,K-ATPase in rats with streptozotocin-induced diabetes.

Overload of reactive oxygen species during diabetes is known to impair cellular homeostasis and to promote deterioration of membrane function in the organism. The aim of the present study was to examine the effect of dietary supplementation with the pyridoindole atioxidant stobadine on functional properties of the renal Na, K-ATPase in diabetic rats. After 16 weeks of streptozotocin-induced diabetes (single intravenous dose of streptozotocin; 55 mg/kg), a significant inhibition (by 35%-42%) of the enzyme was observed throughout the range of NaCl 2-100 mmol/l, probably as an event of altered functional properties of Na,K-ATPase, suggested by the 42% decrease of the V(max) value. Administration of 0.05% (w/w) stobadine in the diet dramatically improved the function of renal Na,K-ATPase in diabetic rats with regard to sodium handling, as suggested by significant stimulation (by 104%-77% in accordance with increasing concentration of NaCl) of the enzyme over the whole NaCl concentration range investigated. This stimulatory effect was accompanied by an increase of V(max) value to the level of nondiabetic rats on standard diet. In conclusion, stobadine was found to antagonise the negative effects of diabetes on the renal Na,K-ATPase, preserving its normal function in regulation of intracellular homeostasis of Na(+) and K(+) ions.