Urine concentration and dilution: effect on red cell survival.

Survival time of 51Cr-labeled red cells was determined in dogs subjected to water restriction excreting concentrated urine and again following a 6-week period of ad lib. water intake. During water restriction, RBC survival was reduced to one-seventh of normal. In rats with untreated diabetes insipidus, 51Cr RBC survival was reduced 30% as compared to the pitressin-treated state. It appears that RBC survival may be influenced by osmotic stress associated with the state of urine concentration and dilution.