AJP - Renal Physiology, Vol 258, Issue 4 1005-F1017, Copyright © 1990 by American Physiological Society
Volume homeostasis in calves with artificial atria and ventricles
C. Westenfelder, F. M. Birch, R. L. Baranowski, J. B. Riebman, D. B. Olsen, G. L. Burns and C. Kablitz
Division of Nephrology, Veterans Administration Medical Center, Salt Lake City 84148.
We examined whether replacement of cardiac atria and ventricles with total
artificial hearts (TAH), a procedure that removes cardiac nerves and all
sources of atrial natriuretic factor (ANF), would cause alterations in
volume homeostasis in awake calves. Preoperatively, extracted plasma
immunoreactive (ir)ANF levels were 13.3 +/- 0.6 and remained
postoperatively at 10.5 +/- 0.4 pg/ml (P less than 0.01). TAH implantation
caused systemic and pulmonary hypertension (P less than 0.01), salt
retention, edema, and significant elevations of plasma renin, aldosterone,
and arginine vasopressin. In intact calves rapid infusion of 6 liters of
normal saline raised irANF levels to 73.7 +/- 6.5 pg/ml (P less than 0.01)
and elicited a large natriuresis and diuresis. No such response to 6 liters
of normal saline was obtained after calves had recovered from TAH
implantation. Reduction of cardiac output (CO) by 50% caused further salt
retention and no change in irANF levels. Elevation of CO back to and 33%
above base line produced only a diuresis, whereas salt retention persisted
and irANF levels remained unchanged. The same maneuvers elicited in
surgical control calves (artificial ventricles only, largely intact atria)
a significant increase in irANF levels and a diuresis and natriuresis. In
conclusion, alterations in volume homeostasis observed after TAH
implantation seem to be the consequence of at least two pathophysiological
mechanisms: 1) functional ANF "deficiency," characterized by apparently
unregulated ANF secretion from noncardiac sites, and 2) cardiac
denervation.
