Renal injury and proteinuria in female spontaneously hypertensive rats

This investigation describes the evolution of functional and morphological changes in the kidney of female spontaneously hypertensive rats (SHR; 5-90 weeks) and control animals of the same genetic strain, Wistar-Kyoto (WKY). Systolic blood pressure in SHR was 162.0 +/- (SD) 14.1 mm Hg up to 45 weeks, then increased to 189.4 +/- (SD) 16.6 mm Hg (50-90 weeks). Blood pressure in WKY controls remained constant (117.8 +/- 13.6 mm Hg, 5-100 weeks). Protein excretion in the SHR was higher than controls (1.5 +/- 0.5 mg/24 h x 100 g BW, 5-100 weeks) from week 30 on. At 90 weeks, excretion rose to 26.1 +/- 9.8 mg/24 h x 100 g BW and is predominately an albuminuria. After 70 weeks superficial tubular fluid albumin concentration in the SHR is significantly increased (p less than 0.001) over controls. Microscopic changes were evident in glomeruli, tubules, interstitium and arterial vessels at 72-90 weeks and demonstrated an increasing gradient of severity from outer to inner cortex. Glomeruli show sclerosis, fibrinoid necrosis and pericapsular fibrosis. Glomeruli studied with a polyanionic stain revealed a marked decrease in staining affinity of deep, compared to superficial glomeruli. The arterial lesions consisted of thickening of the intima and hyperplasia of the media. WKY kidneys were unremarkable. The selectivity of renal injury and proteinuria in the female SHR is similar to that in the male SHR. However, the evolution of these changes is delayed and may be related to a lower blood pressure until 50 weeks of age.