Effect of angiotensin ii receptor blockade on arterial baroreflex
regulation of renal nerve activity in cardiac failure.
Dibona, Gerald F., Susan Y. Jones, and Virginia L. Brooks.
Department of Internal Medicine, University of Iowa College of
Medicine and Department of Veterans Affairs Medical Center, Iowa
City, Iowa 52240 & Department of Physiology, Oregon Health
Sciences University, Portland, Oregon 97201
APStracts 2:0160R, 1995.
In cardiac failure, efferent renal sympathetic nerve activity (ERSNA)
and the activity of the renin-angiotensin system are increased and
arterial baroreflex regulation of ERSNA is attenuated. We examined
the effect of intravenous (iv) and intracerebroventricular (icv)
angiotensin II (AT1) receptor blockade with losartan on the arterial
baroreflex regulation of ERSNA in conscious control (C) and cardiac
failure (CHF) rats. Losartan iv (10 mg/kg = 21.7 [mu]mol/kg iv)
decreased arterial pressure more in CHF than in C (-28 +/- 3 mm Hg vs
-20 +/- 3 mm Hg, P < 0.05). After restoration of arterial
pressure to the pre-losartan value with methoxamine infusion, ERSNA
was decreased more in CHF than C (-23 +/- 4 vs -1 +/- 2 %, P <
0.05). Maximal gain of arterial baroreflex control of ERSNA (Gmax)
was lower in CHF compared to C (-1.94 +/- 0.10 vs -3.78 +/- 0.21 %/mm
Hg, P < 0.05). Losartan iv increased Gmax in CHF (to -3.01 +/-
0.14 %/mm Hg, P < 0.05) but not in C (to -3.56 +/- 0.19 %/mm
Hg). Losartan icv (4.61 [mu]g = 10 nmol icv) did not affect arterial
pressure but decreased ERSNA more in CHF than in C (-13 +/- 2 vs -8
+/- 3 %, P < 0.05). Like losartan iv, losartan icv increased
Gmax in CHF (-2.11 +/- 0.18 to -3.21 +/- 0.30 %/mm Hg, P < 0.05)
but not in C (-3.98 +/- 0.25 to -3.84 +/- 0.22 %/mm Hg). These
results suggest that increased activity of the renin-angiotensin
system contributes to the increase in ERSNA and its abnormal arterial
baroreflex regulation in cardiac failure.
Received 23 January 1995; accepted in final form 7 June 1995.
APS Manuscript Number R54-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.