AJP - Regulatory, Integrative and Comparative Physiology, Vol 260, Issue 4 724-R732, Copyright © 1991 by American Physiological Society
Renal response to 7 days of lower body positive pressure in squirrel monkeys
S. E. Churchill, D. M. Pollock, M. E. Natale and M. C. Moore-Ede
Department of Physiology, Harvard Medical School, Boston, Massachusetts.
The purpose of this study was to characterize the renal response to central
volume expansion using lower body positive pressure (LBPP) in the adult
male squirrel monkey (Saimiri sciureus). Urinary excretion of sodium,
potassium, and water and plasma aldosterone concentrations were measured
during a control day, 7 days of LBPP, and a recovery day. Time control
experiments in the same animals included chair sitting without exposure to
LBPP. Seven monkeys (600-1,000 g) were trained to sit in a specially
designed metabolism chair before chronic implantation of arterial and
venous catheters to facilitate maintenance infusion of saline, monitoring
of vascular pressures, and blood sampling; urine was collected via a
condomlike tube. A cephalad shift in body fluid was induced by applying 20
mmHg of air pressure from the waist down. Urine volume and sodium excretion
were increased significantly (28 to 52 ml/day and 0.4 to 3.5 meq/day,
respectively) during the initial 24 h of LBPP with most of this response
occurring in the first 6-12 h. From the 2nd to the 7th day of LBPP, urinary
excretion rates for sodium and water were not different from chair-sitting
controls. Water and sodium balance significantly decreased from +15 to -12
ml/day and from +1.1 to -2.2 meq/day, respectively, from the control to the
first day of LBPP. This change in balance was not observed in the
time-control group. Removal of the stimulus resulted in a modest
conservation of sodium and water. The renal responses were not associated
with any changes in plasma aldosterone levels.(ABSTRACT TRUNCATED AT 250
WORDS)
