Osmotic control of vasopressin with chronically altered volume states in anephric dogs

Continuous peritoneal dialysis has been used to maintain anephric dogs at chronically sustained low, normal, and high volume states in order to study the long-term interaction of volume and osmotic stimuli in the control of plasma vasopressin (PAVP). Bilaterally nephrectomized dogs were maintained for 1-3 mo with normal plasma sodium and potassium levels and blood urea nitrogen of 70.1 +/- 10.8 mg/dl. During the first month, the dogs were dialysized to each of the three volume states. After each volume state had been maintained for 7 days, an osmotic forcing with intravenous distilled H2O and hypertonic NaCl was performed in the conscious state to quantitate the relationship between plasma osmolality (Posm) and PAVP. During the osmotic forcings left atrial pressure (LAP) averaged -2.4 +/- 0.5, 2.6 +/- 0.8, and 11.9 +/- 1.1 cmH2O; mean arterial pressure averaged 113 +/- 11, 125 +/- 10, and 148 +/- 8 mmHg, both respective for the low, normal, and high volume states. The slope of the normovolemic Posm-PAVP relationship was determined to be 0.047 pg X ml-1 X mosmol-1 X kg-1, and neither the hypovolemic or hypervolemic relationships were significantly different. The results demonstrate two additional points that must be considered in the control of PAVP. First, the severely depressed sensitivity of osmotic PAVP control suggests that either the dialysis procedures or the absence of the kidneys suppressed or eliminated some factor normally important to the secretion of vasopressin.(ABSTRACT TRUNCATED AT 250 WORDS)