Angiotensins promote fluid absorption in the rat ileum after their CNS administration

Angiotensin II (A-II) has been found previously to increase mean arterial pressure (MAP) and enhance fluid absorption in the rat ileum in situ after intracerebroventricular (ICV) administration. In this investigation, the CNS-mediated proabsorptive actions of A-II and other products of the renin-angiotensin system, as well as nonhomologous peptides were further characterized in the urethane-anesthetized rat. At an ICV bolus dose of 1 microgram, angiotensinogen, A-I, A-II and A-III produced significant elevations in MAP, but only A-II and A-III increased ileal absorption significantly above that of saline-treated rats. The ICV administration of other unrelated peptides did not mimic the actions of A-II or A-III. The results suggest that the pressor and ileal proabsorptive actions of angiotensins are mediated through different CNS mechanisms and that these peptides uniquely alter intestinal transport.