Involvement of nitric oxide production in the mildronate mechanism of action

Probable involvement of the NO synthesis activation in the mechanism of action of the anti-ischemic drug mildronate has been tested. Changes in the NO content in different rat tissues (brain cortex, cerebellum, liver, heart, kidneys) were evaluated after administration of mildronate, its structural analogue γ-butyrobetaine (GBB), and neomildronate (mildronate and GBB mixture in ratio 1:1). NO concentration was measured directly with electron paramagnetic resonance method (EPR). It was revealed that mildronate (50 mg/kg, i.p.) triggers the increase of NO level in the brain cortex, cerebellum, and heart 30 min after the drug administration. Administering the nitric oxide synthase (NOS) inhibitor N^ω-nitro L-arginine (50 mg/kg, i.p.) at the same time abolished the NO increase triggered by mildronate. This indicates the necessity of NOS activation to produce NO concentration increase and excludes possible nonenzymatic nature of the mildronate effect. GBB (50 mg/kg, i.p.; 0.5 h) triggered the NO concentration increase in the cerebellum only. Neomildronate action was the most pronounced; the NO concentration increased 30 min after the drug administration and the elevated level of NO was maintained for 2 h. The data provide evidence in favor of hypothesis of gamma-butyrobetaine esterase signalization pathway.