Effects of angiotensin II blockade in the canine puppy under different salt-intake

The objective of this study was to investigate the relationship between the high activity of the renin-angiotensin-aldosterone system (RAAS) and the control of blood pressure and aldosterone in the canine puppy. The effect of the angiotensin II analog saralasin on arterial pressure (MAP), plasma renin activity (PRA), plasma renin concentration (PRC), and aldosterone (PA) was studied in unanesthetized normal, salt-loaded and salt-depleted puppies aged 9 to 30 days. Salt-loading was performed by daily intraperitoneal administration of 10 mEq sodium/kg body weight for 5 days and salt-depletion by furosemide injections. Saralasin infusion, 6 micrograms/kg/min, during 60 min significantly decreased MAP and increased PRC not only in salt-depleted puppies, as has been observed in adult salt-depleted dogs, but also in normal puppies (mean fall, 6.6 mm Hg). Although any developmental changes in the RAAS and MAP and in their relationship could not be ascertained, the fall in MAP during saralasin in normal puppies was significantly correlated to presaralasin renin values (r = 0.76, P less than 0.01, N = 11). PA did not change in both groups of puppies. In salt-loaded puppies saralasin caused no change of MAP, PRC, and PA. We conclude that the high renin levels at young age contribute to the basal arterial pressure in puppies.