Production of hypernatremia and hyperosmolarity in the diabetes insipidus dog infused with Ringer's solution.

SIXCE diabetes insipidus is a disease invariably associated with elaboration of urine hypotonic to plasma, it was hypothesized that the diabetes insipidus dog would deA'elop hypernatremia and plasma hyperosmolarity with sustained infusion of isotonic fluid. To test this hypothesis experiments were undertaken to measure the effects of sustained infusion of Ringer's solution on plasma sodium concentration and osmolarity in diabetes insipidus (DI) and intact dogs. It was found that the DI dog, in contrast to the intact animal, consistently developed significant hypernatremia and plasma hyperosmolarity during infusion of Ringer's solution. It is suggested that assessment of the plasma response to Ringer's infusion may serve as a simple, safe, clinical test for the diabetes insipidus state in man.