Diabetes mellitus in Brattleboro rats: cardiovascular, fluid, and electrolyte status

Because plasma arginine vasopressin (AVP) levels are raised during streptozotocin (STZ)-induced diabetes mellitus (DM), it is possible that AVP contributes to the pattern of change in fluid and electrolyte handling and cardiovascular status after STZ treatment. Therefore we have made daily measurements of cardiovascular and metabolic variables in normal (Long-Evans) and AVP-deficient (Brattleboro) rats treated with saline or STZ. Twenty-four days after STZ, both strains had similar weight loss and increases in fluid intake, but the increase in food intake was greater in Long-Evans than in Brattleboro rats. After STZ, bradycardia developed in both strains, but only Brattleboro rats had reduced blood pressure. Plasma variables were measured 25 days after STZ. Packed cell volume and plasma sodium concentration were reduced in STZ-treated Long-Evans rats compared with saline-treated controls but were unchanged in STZ-treated Brattleboro rats. The results indicate that although AVP deficiency does not seriously affect the ability to maintain fluid and electrolyte balance after STZ treatment, there may be consequences for cardiovascular control.