AJP - Regulatory, Integrative and Comparative Physiology, Vol 253, Issue 2 242-R253, Copyright © 1987 by American Physiological Society
Role of cardiac nerves in response to head-out water immersion in conscious dogs
G. Hajduczok, K. Miki, S. K. Hong, J. R. Claybaugh and J. A. Krasney
The circulatory, renal, and hormonal responses during 100 min of
thermoneutral (37 degrees C) head-out water immersion (WI) were
investigated in conscious intact (INT) and cardiac-denervated (CD) dogs. In
the INT group, both left and right atrial and aortic transmural distending
pressures and left ventricular contractile performance (LV dP/dtmax)
increased, and total peripheral resistance remained unchanged. Cardiac
output (QCO) increased in association with an increase in heart rate and LV
dP/dtmax. Urine flow (V), sodium excretion (UNaV), and osmolal clearance
(Cosmol) all increased, whereas glomerular filtration rate, as indicated by
creatinine clearance (CCr), remained constant. The diuresis and natriuresis
occurred in the absence of any significant changes in plasma levels of
antidiuretic hormone (ADH), aldosterone, or plasma renin activity. The CD
animals showed a similar hemodynamic response except that the increase in
QCO was now associated with an increase in stroke volume and no change in
heart rate or LV dP/dtmax. Although the increase in V was similar in both
magnitude and time course of the INT animals, there was no significant
change in UNaV. Thus there is a striking change in the character of the
response of the denervated group in that the natriuresis is abolished and,
instead, a water diuresis occurred. Free water clearance increased, but no
significant changes in Cosmol or CCr were observed. In addition plasma ADH
levels significantly declined during WI in the CD group. These data
indicate that cardiac receptors are important in determining the nature of
the renal response to WI.
