The Effects Of Different Valsartan-administrating Time On Circadian Rhythm Of Renin-angiotensin System In Rat

Objective: Biological rhythms are a universal phenomenon in living organisms and enable adaptation to the environment. Biological rhythms can be divided into 3 types on the basis of their cycle lengths: 1) circadian (or diurnal) rhythms with a period of approximately 24 hours; 2) ultradian rhythms, with a period significantly shorter than 24 hours (hours, minutes, or even seconds); and 3) infradian rhythms, with a period longer than 24 hours (days, months, or longer). In humans, almost every physiological system has some degree of circadian rhythm. The mechanism behind any of these rhythms can be viewed as endogenous, exogenous, or both.It has been found that blood pressure follows a typical circadian rhythm—it maintains a higher level during the daytime, with peak values between 10 and 12 pm. During the night, blood pressure falls to lower values and reaches its trough value from 3 to 6 am, or 1 to 3 hours before awakening. However, the regulation of blood pressure is a complicated process, during which the renin-angiotensin system (RAS), catecholamines, and endothelial vasoactive substances may play important roles. It is easily to postulate that the changes of...