L–arginine alleviates postmenopausal complications in female rats by stimulating ovarian dopamine beta hydroxylase

Objective: To evaluate the levels of estrogen, albumin and gonadotropins (luteinizing hormone, follicle-stimulating hormone) as well as the activity of dopamine beta hydroxylase (DAß H) in aged female rats treated with nitric oxide precursor L-arginine and neuronal nitric oxide synthase antagonist L-NAME. Methods: A total of 224 Wistar rats (36 weeks old, weighing 250 g) based on a random sampling were divided into the control and experimental groups after Pap smear test. The control group received only saline (1 mL/kg) intraperitoneally (i.p.). The experiential groups were treated with L-arginine (5, 25 and 50 mg/kg, i.p.) and L-NAME (5 and 25 mg/kg, i.p.) for 3 to 21 days, once a day. Blood samples were taken from the rats and the levels of estrogen and albumin and gonadotropins in the serum were monitored by enzyme-linked immunosorbent assay kit, and the ovaries were examined immunohistopathologically for DAßH activity. Results: L-arginine (5 mg/kg) significantly increased estrogen level (P<0.05), which was associated with DAßH activation in the ovaries. L-NAME reduced this effect when administered prior to L-arginine dose. L-arginine caused no significant change in the levels of luteinizing hormone and follicle-stimulating hormone. Except for the lowest dose of L-arginine in the shortest period, albumin levels significantly decreased in other treatments compared to the control group (P<0.05). Conclusions: L-arginine is likely to reduce postmenopausal problems due to an increased nitric oxide level.