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Departments of Internal Medicine and Physiology, University of Iowa College of Medicine and Veterans Affairs Medical Center, Iowa City, Iowa 52242
Central nervous system (CNS) renin-angiotensin activity
influences the basal level of renal sympathetic nerve activity (RSNA) and its reflex regulation. The effect of type 1 angiotensin II (ANG
II)-receptor antagonist treatment (losartan) on cardiac baroreflex regulation of RSNA and renal sodium handling was examined in rats with
cirrhosis due to common bile duct ligation (CBDL). Basal levels of
heart rate, mean arterial pressure (MAP), RSNA, and urinary sodium
excretion were not affected by intracerebroventricular administration
of either losartan or vehicle to CBDL rats. After acute intravenous
isotonic saline loading (10% body wt) in vehicle-treated CBDL rats,
MAP was unchanged and the decrease in RSNA seen in normal rats did not
occur. However, in losartan-treated CBDL rats, there were significant
concurrent but transient decreases in MAP (
20 ± 2 mmHg) and
RSNA (
25 ± 3%). The natriuretic response to acute volume
loading in losartan-treated CBDL rats was significantly less than that
in vehicle-treated CBDL rats only at those time points where there were
significant decreases in MAP. Antagonism of CNS ANG II type 1 receptors
augments the renal sympathoinhibitory response to acute volume loading
in CBDL. However, the natriuretic response to the acute volume loading
is not improved, likely due to the strong antinatriuretic influence of
the concomitant marked decrease in MAP (renal perfusion pressure)
mediated by widespread sympathetic withdrawal from the systemic vasculature.
common bile duct ligation; renal sympathetic nerve activity; renal sodium handling
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