Figure 4. SY exhibits vasorelaxing and anti-hypertensive effects by activating the NO system in SHR in the early stage. Effects of different blockers of vasorelaxing activity of SY (A and B). Comparison of vasorelaxing effects of SY, serine and tyrosine (C). The dose dependency of the vasorelaxing activity of SY (D). SY-induced anti-hypertensive effects were blocked by L-NAME, an NO synthase inhibitor in the early stage (E). Effects of SY on blood pressure in the advanced stage (F). Values are expressed as the means ± SEM (A, n = 4-5; B, n = 4-5; C, n = 3; D, n = 2-3; E, n = 14-16; F, n = 7-8). *P < 0.05 compared with the SY group (A–C). *P < 0.05 compared with the control group (E). #P< 0.05 compared with the SY + L-NAME group.