Prolonged diuretic and saluretic effect of nothofagin isolated from Leandra dasytricha (A. Gray) Cogn. leaves in normotensive and hypertensive rats: Role of antioxidant system and renal protection

Although the acute diuretic effect of nothofagin has been recently demonstrated, its effects after dose-repeated treatment have not yet been explored. For that, male Wistar normotensive (NTR) and spontaneously hypertensive rats (SHR) were orally treated, once a day, with vehicle (VEH: distilled water; 1 ml/kg), hydrochlorothiazide (HCTZ; 10 mg/kg) or nothofagin (NOT; 1 mg/kg). The cumulative diuretic index and urinary electrolytes excretion were measured each 24 h. On the last day of the experiment (7th day), urine, blood and kidney samples were collected for biochemical and molecular analyzes. The urinary volume of both NTR and SHR were significantly increased with the treatment with NOT (from the second to the seventh day of treatment), with final values reaching an increase of 56% and 82%, respectively, when compared with VEH-treated group. This effect was associated with increased levels of urinary excretion of Na⁺ and Cl^-, without any changes on K⁺ excretion. None of the treatments modified urinary pH or density values. Importantly, neither the NOT nor the HCTZ caused any change in body weight following the dose-repeated treatment, and also did not provoke an electrolytic disturbance. Regarding the renal analyzes, when compared with the vehicle-treated NTR group, the activity of superoxide dismutase (SOD) and the reduced glutathione (GSH) levels in kidney homogenates of the SHR group were decreased, while the generation of lipid hydroperoxides were significantly increased. The daily treatment with NOT was able to restore the GSH levels and SOD activity, as well as reduced the lipoperoxidation in the kidney homogenates obtained from SHR Animals. Finally, NOT significantly augmented the levels of nitrite, a marker of nitric oxide production, in the plasma obtained from SHR group when compared with the vehicle-treated only NTR. This study revealed the prolonged diuretic and saluretic effect of nothofagin in normotensive and hypertensive rats. Our data also showed the renal protective effects of nothofagin by the improvement of antioxidative capacity, as well as by the augmented bioavailability of plasma nitric oxide in the hypertensive group.