Increased central angiotensin and osmotic responses in the Ren-2 transgenic rat

We previously demonstrated that the Ren-2 transgenic (TG) rat is sensitive to salt, showing a sodium-induced pressor response. The present studies determined the effect of central stimulation with hypertonic saline (HS) and angiotensin II (Ang Il) on mean arterial pressure (MAP), heart rate (HR), and plasma vasopressin. HS (1 mol/L NaCl, 5 mu L) or Ang II (100 ng, 5 mu L) was injected into the lateral ventricle of conscious male TG and control rats. The pressor responses to HS and Ang were greater in TG than in control rats, increases of 42+/-4 and 41+/-4 mm Hg versus 25+/-3 and 18+/-2 mm Hg (HS and Ang II and TG and control rats, respectively). The TG rats also showed an increased vasopressin response to Ang II, peak levels of 14+/-3 versus 28+/-3 pg/mL (control versus TG rats). HS increased plasma vasopressin levels, although the group responses were not different. HR was not significantly altered by either stimulus. Results demonstrate an increased responsiveness to intraventricular HS and Ang II in Ren-2 transgenic rats, suggesting a relationship between the enhanced angiotensinergic drive and central cardiovascular and vasopressin responses.