Renin secretion in conscious lyon hypertensive rats.
Bertolino, Sylvie, Claude Julien, Isac A. Medeiros, Guy Cuisinaud,
Madeleine Vincent[acute]a, and Christian Barr[theta]s.
D[umlaut]apartement de Physiologie et Pharmacologie Clinique, URA
CNRS 1483, Facult[umlaut]a de Pharmacie, 69373 Lyon Cedex 08,
France
APStracts 3:0205R, 1996.
To characterize the renin secretory profile in Lyon hypertensive (LH)
rats, renin responses to reductions of arterial pressure and b
-adrenoceptor stimulation were assessed in conscious unrestrained LH
(n = 13) and Lyon normotensive (LN, n = 14) rats, under normal-salt
diet. Mean arterial pressure (MAP) in the infrarenal aorta was
recorded beat to beat for 3 h. Then plasma renin concentration (PRC)
was measured (1) in basal conditions, (2) during 10-mmHg stepwise
reductions of MAP down to 60 mmHg using a chronically implanted
aortic inflatable cuff, and (3) during isoprenaline infusion (62.5,
125 and 250 ng.kg-1.min-1 iv). As compared to LN, LH rats had an
elevated MAP (146 3 vs. 111 1 mmHg, P < 0.001) and decreased PRC (4.2
0.6 vs. 8.2 0.8 ng angiotensin (ANG) I.ml-1.h-1, P < 0.001) and
kidney renin content (216 14 vs. 1149 103 g ANG I.h-1.g-1, P <
0.001). Pressure-dependent renin release occurred below 90 mmHg in LN
rats and below 80 mmHg in LH rats, and its sensitivity in the low
pressure range did not differ between strains. Isoprenaline-induced
increases in PRC were weaker (P < 0.01) in LH than in LN rats.
In additional LH and LN rats (n = 6-8), acute ANG II subtype 1
-receptor blockade with losartan (20 mg.kg-1 followed by 10 mg.kg-1.h
-1 iv, for 2 h) induced lesser (P < 0.001) PRC increases in LH
than in LN rats. Renin responses to isoprenaline remained blunted (P
< 0.01) during losartan infusion in LH rats. We conclude that in
LH rats, renin secretion is independent of MAP in the range of its
spontaneous variations and is poorly responsive to b-adrenoceptor
stimulation, which alteration cannot be explained by an enhanced
feedback inhibition by ANG II.
Received 6 December 1995; accepted in final form 9 May 1996.
APS Manuscript Number R769-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 17 June 96