Renal function of baboons (Papio hamadryas) with a remnant kidney, and impact of different protein diets.

To assess progression of renal disease and the effects of protein intake in a species phylogenically close to man, 10 young adult baboons (Papio hamadryas) were subjected to 20 to 30% infarction of the left kidney and, two months later, to right nephrectomy. They were then randomized to a synthetic diet containing either 8% or 25% protein. Hemodynamic and metabolic measurements were obtained in awake animals every four months. Baseline mean blood pressure, inulin clearance, protein and urea nitrogen excretion in intact animals on 15% protein averaged 75.5 +/- 3.5 (SE) mm Hg, 42.9 +/- 2.7 ml/min, 52 +/- 4.3 mg/24 hr, and 3.8 +/- 0.4 g/24 hr, respectively. At 12 months, values in the same baboons with a remnant kidney on 8% versus 25% protein averaged 100.6 versus 96.7 mm Hg, 29.2 versus 54.9 ml/min (P less than 0.01), 111 versus 108 mg/24 hr, and 3.4 versus 11.0 g/24 hr (P less than 0.001), respectively. Electron microscopic examination of renal biopsies obtained eight months after nephrectomy was normal but for slightly increased mesangial matrix in three animals. Thus, blood pressure increased (P less than 0.01), proteinuria doubled (P less than 0.01) and adaptations in GFR developed within four months of renal mass reduction, without significant changes occurring between four and 12 months. The adaptations in GFR were markedly attenuated by low protein intake. Further follow-up is necessary to assess progression of renal disease and the impact of different protein diets.