Aim: 

The aim of this study was to assess the effect of the pyridoindole antioxidant stobadine on diabetes-induced changes of Na,K-ATPase, especially those concerning the utilisation of its substrate ATP.

Methods: 

Diabetes type-1 was induced in 8-week-old rats, by a single i.v. injection of streptozotocin (STZ) in a dose 55 mg.kg^-1. ATP-kinetics of Na,K-ATPase was estimated by measuring the hydrolysis of ATP.

Results: 

Sixteen weeks of streptozotocin-induced diabetes was followed by decrease of the enzyme activity. This effect was emphasised in the presence of higher concentrations of ATP and in the presence of 8 mmol•l^-1 ATP represented 20%. It might be a consequence of altered functional properties of Na,K-ATPase as suggested by 20% decrease of the V _max (maximum velocity) value along with decrease of the K_m value by 20% (K_m-concentration of ATP necessary for half-maximal activation of the enzyme). Administration of 0.05% (w/w) stobadine in the diet to diabetic rats improved the function of renal Na K-ATPase with respect to utilisation of ATP as suggested by significant increase of the enzyme activity in the whole concentration range of ATP investigated as a consequence of V_max elevation to the level comparable to absolute controls.

Conclusion: 

Stobadine may play a positive role in restoring the functional properties of renal Na,K-ATPase, especially concerning the utilisation of energy derived from hydrolysis of ATP, improving thus the maintenance of ionic homeostasis during diabetes.

This work was supported by the Slovak Grant Agencies (grant No. APVT 51-027404, APVT 20-020802, VEGA 2/2050/22)