Metabolic Adjustments In Response To Graded Exercise Depends On Central Angiotensin At1-Receptors

To asses the influence of central angiotensin AT1 receptors on metabolic adjustments in rats during graded exercise on a treadmill, 2 μL of NaCl (Sal) or losartan (Los; 60 nmol) were intracerebroventricularly injected before running until fatigue (starting at 10 m/min, 1 m/min increment every 3 min until fatigue, 10% inclination). Oxygen consumption (VO2) was measured and mechanical efficiency (ME) calculated (n=6). The same protocol was used to collect blood samples through a jugular catheter (n=7). Plasmatic concentrations of glucose, lactate and free fatty acids (FFAs) were determined. During the first two steps of exercise, a similar increase in VO2 and equal ME were observed in both groups. Thereafter, VO2 continued to increase, but at a higher rate in Los-treated animals, leading to a 34% reduction in ME in these animals (p<0.01). Los-treated rats also showed a fast hyperglycemic response, already seen at low exercise intensities as 20% of maximal work. Higher lactate and FFAs levels followed this hyperglycemic response. The data shows that AT1-receptor blockade during graded exercise increases metabolic cost, leading to decreased ME, hyperglycemia and higher FFA mobilization at lower levels of exercise intensities. We conclude that angiotensinergic blockade results in higher and premature sympathetic activation, shifting energy balance during graded exercise. Supported by CNPq, FAPEMIG