Abstract TAC227: The Effect of Umami Components, Glutamate and Aspartate on Blood Pressure in Normotensive and 2-kidney, 1-clip Renovascular Hypertensive Rats

Introduction: We previously observed a decrease in blood pressure (BP) by intake of Saccharina japonica (SJ) or the extract of SJ (SJE) diet in 2-kidney, 1-clip renovascular hypertensive (2K1C) rats. SJ is rich in glutamate (Glu) and aspartate (Asp), which are the umami taste of amino acids. Over 70% (70 of 100) of the SJ components such as Glu and Asp are eluted into the SJE from SJ. It was reported that people with a high dietary intake of Glu have lower BP in epidemiological studies. The intake of Asp was reported to reduce BP in Dahl salt-sensitive rats. Therefore, we hypothesized that the intake of Glu and Asp reduces BP in 2K1C rats. To test the hypothesis, we observed BP in renovascular hypertensive rats fed Glu. Then, we also observed the effect of nitric oxide synthase (NOS) inhibitors in order to investigate the involvement of NOS in the mechanism. We also observed the BP in 2K1C rats ingested Asp. Methods: Male Sprague-Dawley rats (6 wks) were treated with sham surgery (SHAM) or left renal artery clipping (2K1C). These rats were fed a control diet (C) or a Glu-supplemented diet (G), with tap water (V) or neuronal NOS (nNOS) inhibitor (7NI). In another experiment, SHAM or 2K1C rats were fed a control diet (C) or a Asp-supplemented diet for 6 weeks, respectively. Systolic BP (SBP) and mean arterial BP (MAP) were measured. Results: SBP of 6 weeks after the surgery was significantly increased in the 2K1C-C group than in the SHAM-C group (111±6 vs 163±3 mmHg, p < 0.05). In the SHAM and 2K1C of G groups, BP significantly increased compared with each C group (111±6 vs 147±3 and 163±3 vs 177±7, p < 0.05). In group C, SBP of SHAM-7NI was significantly higher than SHAM-V(152±4 vs 111±6, p < 0.05) but not in 2K1C groups. On the other hands in the G groups fed a Glu diet, there was no difference in SBP between the SHAM-7NI and -V, but 2K1C-7NI was significantly lower than 2K1C-V (149±4 vs 147±3 and 165±4 vs 182±7, p < 0.05). Besides, 2K1C-Asp decreased compared with 2K1C-C (147±4 vs 161±4 mmHg, p < 0.05), while there was no difference among SHAM groups. The MAP was observed to be consistent with those of SBP. Discussion and conclusions: These results suggest that Glu increases BP in renovascular hypertensive rats a mechanism involving the activation of nNOS, whereas that significantly increase BP in normotensive SHAM rats without involving the nNOS activation. In contrast, Asp is probably attenuate hypertension in 2K1C renovascular hypertension.