Radioimmunoassay measurement of albumin in urine is a valid method for monitoring analbuminemia in rats.

Plasma and urinary albumin levels, urinary creatinine and urine volumes were measured at two-week intervals in Nagase analbuminemic rats (NAR) of either sex at ages from 42 to 154 days. Age matched Sprague Dawley (SD) rats were used as controls. Plasma concentrations of immunoreactive albumin (iALB) in NAR ranged from 0.007 +/- 0.002 to 0.023 +/- 0.003 mg/ml, and were lower in younger rats. In SD rats, plasma iALB concentrations ranged from 18.9 +/- 1.0 to 46.2 +/- 6.4 mg/ml. Urinary iALB output in NAR was less than 0.05 micrograms/mg creatinine measured over a 24 hr period, whereas it was greater than 20 micrograms/mg creatinine in the SD rats. Measurement of urine iALB concentrations in the NAR colony appears to be a reliable and a non-invasive method for monitoring the persistence of hypoalbuminemia.