AJP - Heart and Circulatory Physiology, Vol 242, Issue 6 1056-H1064, Copyright © 1982 by American Physiological Society
Effects of left atrial stretch in cardiac-denervated and intact conscious dogs
D. C. Fater, H. D. Schultz, W. D. Sundet, J. S. Mapes and K. L. Goetz
We monitored cardiovascular and renal function in conscious dogs with
surgically denervated hearts during two experimental procedures: 1)
inflation of a balloon in the left atrium and 2) intravascular volume
expansion. The results obtained were compared with results from identical
experiments on sham-operated control dogs. Left atrial balloon inflation in
the sham-operated dogs produced an increase in left atrial pressure, heart
rate, urine flow, and sodium excretion; central venous pressure decreased.
These changes were absent in the cardiac-denervated dogs. Infusion of 6%
dextran in isotonic saline (16% of estimated blood volume) increased the
heart rate significantly in the control dogs but not in the
cardiac-denervated dogs; other hemodynamic measurements were comparable in
the two groups. Urine flow and sodium excretion increased significantly in
both the cardiac-denervated and control dogs; the responses did not differ
significantly between the two groups. These experiments demonstrate that
inflation of a balloon in the left atrium of a conscious dog elicits
diuretic and natriuretic responses that are dependent on intact cardiac
neural pathways, presumably specifically dependent on afferent neural
impulses from left atrial receptors. On the other hand, an increase in
circulating blood volume induced by the intravenous infusion of an
isotonic, isoncotic solution elicits diuretic and natriuretic responses in
the cardiac-denervated dog that are similar to the renal responses produced
in a control dog. Thus, although cardiac receptors are capable of eliciting
reflex changes in both hemodynamics and renal function, it is not clear
what role they play in mediating the renal responses evoked by increases in
blood volume.
