A15605 Low sodium intake alleviates noradrenaline-induced vasoconstriction of the mesenteric small artery in Dahl salt-sensitive rats

Objectives: To study the effect of low sodium diet on the functional vasoconstriction of the mesenteric small artery (MSA) in Dahl salt-sensitive (DS) rats. Methods: 24 8-week male DS rats were randomized into four groups: normal sodium (NS), low sodium (LS), high sodium (HS), and high sodium followed by low sodium (HL) group. The first three groups were given 12-week diet with 0.6%, 0.3% and 8% of NaCl respectively, while the HL group was given 6-week high sodium diet followed by 6-week low sodium diet. After 12-week diet intervention, the diameter of MSA was recorded in situ and in vivo before and after NA injection (10 μg/kg) by a high-speed camera (GigaView camera, USA) with a microscope (BX51W1, OLYMPUS, Japan). Vasoconstriction was presented as the reduction of MSA diameter after NA injection divided by the diameter at baseline. Results: After 12-week diet intervention, compared with that in NS group, NA-induced vasoconstriction of MSA significantly enhanced in HS (50.48 ± 11.34% vs. 22.92 ± 2.43%, P = 0.0005) and HL group (34.13 ± 10.27% vs. 22.92 ± 2.43%, P = 0.0423). The percentage ratio was significantly lower in HL than that in HS group (34.13 ± 10.27% vs. 50.48 ± 11.34%, P = 0.0251). The duration of vasoconstriction was significantly longer in HS than that in NS (51.6 ± 17.5 s vs. 24.7 ± 3.7 s, P = 0.0086) and HL group (26.0 ± 5.5 s vs. 24.7 ± 3.7 s, P = 0.0086), while in LS, was shorter than that in NS group (16.2 ± 3.2 s vs. 24.7 ± 3.7 s, P = 0.0016). Conclusion: Change from high to low sodium diet improved the vasoconstrictive function of MSA in DS rats. Our results emphasized the significant role of sodium restriction in overcoming the hyperresponsiveness of small artery to catecholamine in hypertension.