Sequential alterations in clinical biochemical indicators of renal function in 5/6 nephrectomized rats--basic study for renal toxicity using 5/6 nephrectomized rats.

It has been established that progression of renal lesions in 5/6 nephrectomized rats, in which the total right kidney was removed and two poles of the left kidney were excised surgically, and are used as an animal model of renal failure in man, can be morphologically divided into three stages. In the present study, for establishing a renal toxicity study using this animal model on the physiological side, changes of biochemical parameters were sequentially investigated in 20 male 5/6 nephrectomized Wistar rats until 26 weeks after nephrectomy. Creatinine clearance (CLcre) and water as well as electrolyte reabsorption (FRwater and FR Na, K, Cl) were reduced at weeks 2-4, then increased slightly from weeks 6 to 10, and reduced again thereafter. On the contrary, urinary protein was elevated throughout the experimental period, while albumin fraction was increased after week 2 and low-molecular tubular protein increased after week 6 by electrophoresis. Urinary LDH also demonstrated high levels throughout the observation period, but ALP only increased after week 18. The present study thus confirmed that renal function after 5/6 nephrectomy is indeed changed in three stages with clinical biochemical parameters, especially CLcre and FR Na, K, Cl being good indicators to distinguish the three stages of glomerular and tubular dysfunction, respectively. In addition, urinary protein-fractions by electrophoresis in this animal model were examined for the first time, proving useful approach to glomerular and tubular dysfunction.