ASSESSMENT OF THE ACCURACY OF QUANTITATIVE URINE COLLECTION IN MINK (MUSTELA-VISON) USING OSMOTIC PUMPS FOR CONTINUOUS RELEASE OF P-AMINO-HIPPURIC ACID AND INULIN

A method is described to assess the accuracy of quantitative collectio n of urine in small experimental animals using implanted Alzet(R) osmo tic pumps for continuous release of specific urinary markers. The nomi nal pumping rate (10.00 +/- 0.15 mu l/h; mean +/- SEM) of 10 osmotic p umps was verified (9.96 +/- 0.12 mu l/h) in a 10-day in vitro assay in isotonic saline at 39.0 degrees C. Ten adult female mink (1100 +/- 34 g) had a 2-ml osmotic pump implanted intraperitoneally for 7 days whi le maintained in metabolic cages on a conventional mink diet. In 5 min k the pumps contained [H-3]-labelled p-aminohippuric acid (PAH) only. The remaining 5 animals received a pump containing [H-3]-PAH and [C-14 ]-labelled inulin. The experiment was well tolerated by all animals. I n fed animals, the amount of urine collected per day was not influence d by the osmotic pumps, whereas 24 h of fasting (water allowed) caused a dramatic fall in urinary volume. In 4 consecutive 24-h collections of urine (n = 10 animals) the recovery of [H-3]-PAH was 70.8 +/- 3.6% (range: 52.0-87.2%), and urinary plus faecal water (=total) recovery o f [H-3]-PAH averaged 77.0 +/- 3.7% (range: 60.3%-94.3%). For [C-14]-in ulin (n = 5 animals) the urinary and total recoveries were 68.4 +/- 2. 2% and 77.2 +/- 2.4%, respectively. in urine the C-14 to H-3 counts-ra tio was almost identical to that of the infusion solution, indicating that metabolic decomposition of the markers was negligible. The result s indicate that the daily recovery of suitable urinary markers, releas ed by implanted osmotic pumps, provides a reproducible and valid measu re of the accuracy achieved in quantitative collection of urine in min k and probably also in other animal species. Hence, this technique may be useful in future studies on animal nutrition and/or drug dispositi on.