Influence of feeding schedules on the chronobiology of renin activity, urinary electrolytes and blood pressure in dogs

The contribution of the renin–angiotensin–aldosterone system (RAAS) to the development of congestive heart failure (CHF) and hypertension (HT) has long been recognized. Medications that are commonly used in the course of CHF and HT are most often given with morning food for the sake of convenience and therapeutic compliance. However, biological rhythms and their responsiveness to environmental clues such as food intake may noticeably impact the effectiveness of drugs used in the management of cardiovascular disorders. Only sparse information about the effect of feeding schedules on the biology of the RAAS and blood pressure (BP) is presently available. Two studies were designed to explore the chronobiology of renin activity (RA), BP, renal sodium (UNa,fe) and potassium (UK,fe) handling in relation to meal timing in dogs. In a first experiment (Study a), blood and urinary samples for measurement of RA, UNa,fe and UK,fe were drawn from 18 healthy beagle dogs fed a normal-sodium diet at either 07:00, 13:00 o...