AJP - Heart and Circulatory Physiology, Vol 263, Issue 4 1017-H1020, Copyright © 1992 by American Physiological Society
Altered pressure-volume relation of right atrium and venoatrial junction in diabetic rats
M. B. Patel, P. L. Zhang, A. C. Patel and K. P. Patel
Department of Physiology and Pharmacology, University of South Dakota School of Medicine, Vermillion 57069.
Previous studies have indicated a blunted volume reflex in diabetic rats.
This alteration of the volume reflex may be due to differences in
distensibility of the right atrium and venoatrial junction, which contain a
large number of volume receptors. This study was designed to determine
whether the distensibility of the right atrium and venoatrial junction is
altered in the diabetic rat. The distensibility was assessed by measuring
the stiffness constants [slope of pressure-volume (P-V) curve] of the right
atrium and venoatrial junction in 2-wk streptozotocin-induced diabetic
rats. The P-V data of the right atrium and venoatrial junction were
measured in control and diabetic rats over a range of 0-10 mmHg by infusion
of isotonic saline in KCl-arrested, in situ hearts. Similar P-V data also
were determined in an additional group of diabetic rats under daily insulin
treatment, which normalized plasma glucose. The mean slope of the P-V curve
of the right atrium and venoatrial junction in the diabetic rats was
significantly greater than the mean slope of the control and
insulin-treated diabetic rats. The results indicate that diabetic rats have
stiffer right atria and venoatrial junctions, which may reduce stimulation
of the volume receptors to acute volume loading. In addition, the increased
stiffness in the diabetic rats was prevented by chronic insulin treatment.
An altered afferent limb of the volume reflex in diabetic rats contributing
to blunted diuretic and natriuretic responses to volume loading may be due
to these documented changes in the distensibility of the right atrium and
venoatrial junction.
