ET B receptors contribute to synchrony between blood pressure and other peripheral circadian rhythms in the Sprague-Dawley rat.

Maintaining temporal coordination of physiological function is essential for good health. To determine how the endothelin axis regulates the timing of blood pressure (BP) and key physiological rhythms, we monitored circadian rhythmicity of BP and other variables by telemetry in male and female Sprague Dawley rats with or without chronic ETB receptor blockade (A-192621). Rats were maintained under constant dark conditions to ensure a free running status of the circadian clock. Rats were divided into groups being fed either normal salt (NS) or high salt (HS) diets starting the day of release into constant darkness. After one week, a subset of rats was given A-192621 in the food for two weeks. HS diet exacerbated amplitude of mean arterial pressure (MAP) in ETB antagonist treated rats. ETB antagonism was sufficient to delay MAP rhythms either diet. There were no changes in amplitude of heart rate (HR) or body temperature resulting in desynchrony between the phases with MAP. Rats fed a HS diet without antagonist also displayed desynchrony among all peripheral rhythms. Together these data support the notion of the endothelial system regulating BP rhythms and maintaining synchrony with peripheral physiological rhythms.