Clinical and pathogenic studies on aged polyuria in the IVCS strain of mouse

As aged polyuria is often observed in the IVCS strain of mouse, biochemical and histological studies were undertaken in order to clarify its etiology. Polyuria was observed at 7-8 months of age, and significant increases in water intake and urine volume were noted at 10-11 months of age. IVCS strain mice over one year old showed water intakes and urine volumes about five to six times greater than those in DDI strain mice. The osmolarity of urine excreted from polyuric mice was low compared with DDI strain mice, and elevations of sodium and potassium excretion were observed at an early stage of polyuria. At a more advanced stage of the disease, proteins of low molecular weight were excreted in most animals. Furthermore, depression of kidney response to ADH was recognized soon after onset of polyuria compared with normal IVCS strain mice. Thus, polyuria observed in IVCS strain mice may result from a functional defect of the renal tubules. In addition, significant deposition of amorphous substances, especially in the liver, kidney and spleen, occurred almost in parallel with polyuria. From these findings, it is obvious that mice of the IVCS strain exhibit characteristic polyuria and storage disease as they age.