Behavior of renin angiotensin aldosterone axis during pulling exercises in euhydrated and dehydrated horses

The influence of hydration prior to exercise on hormonal response to exercise was investigated in horses, divided into two groups, control (n = 11) and dehydrated (n = 53). They were also classified according to their body weight in A (⩽350 kg), B (351–450 kg) and C (⩾451 kg). Horses covered 60 m on a track pulling a carriage loaded with 2, 2.25 and 2.5 times their body weight, for A, B and C. Blood samples were taken at rest, after exercise and during recovery. Electrolytes, albumin, renin, angiotensin and aldosterone concentrations were measured. Dehydrated and control horses had higher aldosterone in category A than B and C. Dehydrated horses presented higher albumin, Na, K, Cl, angiotensin and aldosterone in most of the sampling times. There were no differences in renin associated with body weight category, hydration status and exercise. In dehydration, the response of aldosterone to exercise was higher than in euhydration.