Oral urine recycling in diabetes insipidus (DI) rats--the role of the gut in absorption of some urinary components.

Brattleboro rats with diabetes insipidus (DI) will, if no other fluid is offered, drink their own previous day's urine. Such oral urine-recycling, where normal elimination is effective only in 15%, does not result in clinical or laboratory signs of uraemia even after 20 days. Serum electrolytes and creatinine remained normal, serum osmolarity and urea were slightly raised, but none of the parameters measured could be classified as uraemic. Extrarenal excretion of electrolytes increased. It is suggested that when the excreted load is represented to the organism from the gut lumen (as opposed to re-presentation into the peritoneal cavity or cessation of renal function) the gut wall serves a protective function by not reabsorbing significant portions of both the inorganic and organic loads in the urine. More detailed analysis will be required to establish this suggestion.