Control of renal and mesenteric conductance during hemorrhage in conscious hypertensive rabbits

Control of renal and mesenteric conductance during hemorrhage was examined in conscious renal-wrap hypertensive rabbits. Hemorrhage was performed under control conditions and during blockade of 1) vasopressin (AVP) and angiotensin II (ANG II); 2) the autonomic nervous system (ANS); and 3) the ANS, AVP, and ANG II. We hypothesized that hypertensive rabbits would have impaired hormonal and autonomic control of renal and mesenteric conductance. When the ANS was intact, hypertensive rabbits had an impaired ability to control blood pressure but no impairment in renal and mesenteric vasoconstriction during hemorrhage. When the ANS was blocked, AVP- and ANG II-mediated control of blood pressure was not observed during hemorrhage but was observed during a 2-min pause after hemorrhage was terminated. During this pause (ANS blocked), the hypertensive rabbits did not exhibit an impaired vasoconstriction of the renal or mesenteric beds. We conclude that, although the hypertensive rabbits had an impaired ability to control blood pressure during hemorrhage, this was not associated with an impaired ANS- or AVP- and ANG II-mediated control of renal or mesenteric vascular conductance.