Hormonal and renal response to plasma volume expansion in the primate Macaca mulatta

The purpose of this study was to investigate the hormonal and renal response to plasma volume expansion in the ketamine-anesthetized rhesus monkey. The blood volume was determined in nine animals and found to be 6% of the body weight. Six monkeys received isoncotic isotonic fluid amounting to 25% of the blood volume. Plasma volume expansion led to significant decrease in the plasma concentrations of antidiuretic hormone (46.7%) and aldosterone (78.4%) as well as plasma renin activity (50.0%). The mean arterial pressure, plasma osmolality, and plasma concentrations of Na+ and K+ were unaffected by plasma volume expansion. However, renal plasma flow, glomerular filtration rate, the excretion of Na+ and K+, and urine flow increased. It was concluded that, in the ketamine-anesthetized rhesus monkey, circulating hormones contribute to blood volume homeostasis presumably through a neural mechanism similar to that observed in dogs and humans.