| Abstract: | Objective To test the following three hypotheses: ①plasma sodium concentration displays a 24-hour rhythm; ②the circadian rhyt hm of plasma sodium is disrupted in SHR fed a basal NaCl diet; ③high NaCl diet elevates plasma sodium concentration and may lead to an increase in mean arteria l pressure (MAP) of SHR. Methods After having been instrumen ted with arterial catheter at 9 weeks of age, all rats (Spontaneously Hypertensi ve Rat, SHR; Wistar-Kyoto Rat, WKY) experienced two experimental protocols, th e mean arterial pressure and heart rate were monitored and the blood samples als o been analysed for sodium contents. Results On basal NaCl diet, plasma sodium concentrations in SHR w ere significantly higher than those of WKY at almost every time point measured a nd the plasma sodium concentration and MAP rhythms were in nearly opposite phase s; on high NaCl diet, the MAP and plasma sodium rhythms were essentially opposit e in WKY. In SHR, the plasma sodium rhythm was inversely related to the MAP rhyt hm. Conclusion Plasma sodium displays a significant circadian rhythm in rats. The high NaCl diet disrupts the normal plasma sodium circadian rhythm only in SHR. |
