Age-related pathophysiological changes in rat oligomeganephronic hypoplastic kidney.

Rat male hypogonadism (hgn/hgn) is accompanied by oligomeganephronic hypoplastic kidney (HPK), in which each kidney contains one quarter the number of nephrons present in a normal kidney. The nephrons of the HPK are extremely hypertrophied. These characters were apparently common to human oligomeganephronia (OMN). To determine the age-related changes in renal pathophysiology in HPK rats, we measured several parameters of renal function at 70 days, 140 days, 210 days, and 280 days of age. At all time points, relative kidney weight was significantly smaller in HPK rats than in their normal litter mates. In HPK rats, both polyuria and polydipsia became more severe with advancing age. Although creatinine clearance (Ccr) and urinary nitrogen clearance (Cun) were significantly lower in HPK than in normal rats, the values did not decrease with age. A severe form of glomerulosclerosis, as well as interstitial infiltration and cystic dilation of tubules with proteinaceous luminal casts, was observed in the inner cortex and medulla of HPK rats at advanced age. In these animals the surface glomeruli retained their functional architecture but were hypertrophied. Both mean blood pressure (MBP) and proteinuria became more elevated with age in HPK rats, and their urine samples included considerable amounts of high molecular weight protein. These results suggest that the HPK rat is a suitable model of human OMN.