Vasopressin in Rats With Genetic and Streptozocin-Induced Diabetes

Rats were administered streptozocin (STZ; 50 or 75 mg/kg i.v., tail vein) or vehicle. Approximately 2 wk later, venous and arterial catheters were implanted for subsequent (24 h later) vasopressin, electrolyte, and hemodynamic measurements. STZ-induced diabetic (STZ-D) rats demonstrated a dose-dependent increase in the plasma glucose concentration, plasma osmolality, and plasma vasopressin concentration. Mean arterial blood pressure (MABP) was unchanged, but heart rate was reduced. Diabetes-prone BB rats, maintained on or withdrawn from insulin treatment for 24–48 h, and diabetes-resistant rats were instrumented and studied as above. Spontaneous-diabetes–prone rats demonstrated increases in plasma glucose concentration and plasma osmolality similar to STZ-D rats but had significantly greater plasma vasopressin concentrations. The significant decrease in MABP observed in these animals probably contributed to the enhanced vasopressin response. We conclude that both osmotic and cardiovascular parameters play important roles in vasopressin secretion in diabetic rats.