Midwall left ventricular mechanics in rats with or without
renovascular hypertension: effect of different sodium intakes.
Simone, Giovanni De, Richard B. Devereux, Massimo Volpe, Maria J. F.
Camargo, Donald C. Wallerson, John H. Laragh.
The Department of Medicine and the Hypertension Center, The New
York Hospital-Cornell Medical Center. Supported in part by grant
HL18323 from the National Heart, Lung and Blood Institute, Bethesda,
Maryland
APStracts 2:0296H, 1995.
Supranormal left ventricular (LV) function has been reported in one
-kidney, one clip (1K1C) and two-kidney, one clip (2K1C) Goldblatt
hypertension. However, this finding might be at least partially due
to mis-matching endocardial rather than midwall fractional shortening
to mean end-systolic stress. Accordingly, relations of
echocardiographic endocardial and midwall shortening to
circumferential end-systolic stress were calculated in 40 Wistar rats
on 0.4%NaCl (r=-0.92, SEE=4.3% and r=-0.62, SEE=3.2%, both
p<0.0001). Midwall shortening as a % of predicted was related to
LV chamber diameter in normal animals (r=0.56, p<0.0001).
Endocardial and midwall shortening were compared as percent of the
normal values predicted from wall stress in 34 2K1C and 19 1K1C on
0.4%Na+, 8 to 9 weeks after surgery. Use of midwall shortening
reduced the proportion of these hypertensive rats with supranormal
observed/predicted shortening ratio from 28% to 7.5% (p<0.0001).
Salt-deprived and high-salt diets (0.0035% NaCl and 4% NaCl) were
given to 16 and 18 additional controls, 9 and 7 2K1C, and 7 and 7
1K1C. Salt-deprived sham animals had greater endocardial and midwall
shortening (106+/-7% and 111+/-10% of predicted, both p<0.002)
than sham rats on 0.4%NaCl, whereas 4% NaCl had no effect. Five of 16
salt deprived sham rats had supranormal observed/predicted midwall
shortening ratios for LV chamber size, suggesting an enhanced
inotropic state. Salt-deprived and high salt diets had negligible
effects on LV performance in Goldblatt rats. Thus, use of midwall
shortening reduces the proportion of renovascular hypertensive rats
with apparently increased LV function. Salt-deprivation stimulates LV
myocardial function in normal rats, independently of chamber
dimension (i.e. an indirect measure of preload), but does not
influence LV performance in Goldblatt hypertension, 8 weeks after
renal artery clipping.
Received 3 November 1994; accepted in final form 10 July 1995.
APS Manuscript Number H985-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.