Anti-hypertensive effects of shichimotsukokato in 5/6 nephrectomized Wistar rats mediated by the DDAH-ADMA-NO pathway

Shichimotsukokato (SKT) is a Kampo formula, comprising astragalus root, phellodendron bark, rehmannia root, peony root, cnidium rhizome, Japanese angelica root, and uncaria hook. It is prescribed to hypertensive patients who complain of a sensation of a rush of blood to the head, shoulder stiffness, tinnitus, and dull headache. We investigated the effects of SKT on renal hypertension in Wistar rats subjected to a 5/6 nephrectomy (Nx). Systolic blood pressure (SBP) increased markedly after surgery and remained high in the Nx rats. Oral treatment of SKT extract at dosages of 0.75 and 1.5 g/kg/day (corresponding to 5- and 10-fold human dosages, respectively) caused a significant suppression of the increase in SBP in Nx rats. Plasma concentrations of nitric oxide (NO) were marginally lower and asymmetric dimethylarginine (ADMA) significantly higher in the Nx rats than in sham-operated rats. SKT administration caused a significant counteraction of these changes. Finally, we evaluated the levels of protein methyltransferase (PRMT), an enzyme that catalyzes the production of ADMA, and the levels of dimethylarginine dimethylaminohydrolase (DDAH), an enzyme involved in the degradation of ADMA, in the remnant kidney. Neither Nx nor SKT treatment affected PRMT-1 or DDAH-1 levels. DDAH-2 levels were reduced significantly in the Nx rats compared with the sham-operated rats. SKT treatment significantly ameliorated this decrease in the DDAH-2 levels. It is considered that SKT reduced blood pressure in the renal hypertension rat model, mediated, at least partially, by the DDAH-ADMA-NO pathway.