Relationship between blood pressure level, renal histopathological lesions and plasma renin activity in fawn-hooded rats.

The fawn-hooded rat (FH rat) develops hypertension accompanied with focal and segmental glomerulosclerosis and proteinuria, resulting in premature death. In a first experiment the relationship between renal lesions and blood pressure at various ages was investigated. In a second experiment blood pressure was measured weekly from 10 to 38 weeks of age in a number of male FH rats, followed by examination of renal tissues at 40 weeks of age. Plasma renin activity (PRA) had also been determined in individual FH rats. FH rats aged 4.5 weeks had no renal morphological abnormalities. The severity of the glomerulosclerosis increased with age and showed a positive relationship with blood pressure. The scores of the proteinaceous tubular casts also increased with age and they, too, showed a positive correlation with blood pressure. The severity of glomerulosclerosis and proteinaceous casts at 40 weeks of age was related positively to the course of blood pressure throughout life. The final blood pressure level showed a positive correlation with final PRA values. Only FH rats with malignant nephrosclerosis had high PRA values. The renal glomerular and vascular lesions in the FH rat, most likely caused by the hypertension, progressively deteriorate to malignant nephrosclerosis. At that stage PRA values are increased and may be contributing to the development of renal vascular lesions and acceleration of the hypertension.