EFFECTS OF WATER DILUTION, HOUSING, AND FOOD ON RAT URINE COLLECTED FROM THE METABOLISM CAGE

The objective of the study reported here was to investigate three fact ors that may affect the amounts of water consumed and urine excreted b y a rat in the metabolism cage: water dilution, housing, and food. You ng F344/N rats (eight per group) were used for all experiments, Food w as withheld from rats before each 16-h urine collection, then rats wer e transferred into a metabolism cage. For trial A (water dilution), ur ine was collected from rats supplied with dyed water (0.05%, vol/vol). This was repeated three times over a 2-week period. Dye in water or: urine was quantified, using a spectrophotometer. For trial B (housing) , rats were individually housed in wire cages for 3 weeks before the f irst urine collection. Then they were group housed in the solid-bottom cage (four per cage), After 2 weeks of acclimation, urine collection was repeated. For trial C (food), one group of rats was provided with food, the other was not, during urine collection, About 8% of urine sa mples of small volume (less than or equal to 3 ml) from trial A were c ontaminated with drinking water up to 13% of volume. The average urine volume associated with individual housing was approximately twice as large as that associated with group housing. When food was provided du ring urine collection, rats consumed similar amounts of water but excr eted significantly smaller amounts of urine than did rats without food . It was concluded that water dilution of a urine sample from a sipper bottle is relatively small; rats individually housed in wire caging b efore urine collection can consume and excrete a larger quantity of wa ter, compared with rats group housed in solid-bottom cages; and highly variable urine volumes are, in part, associated with lack of access t o food during urine collection.