Effects of an acute protein load on urinary albumin excretion in kidney donors

In six kidney donors with normal baseline urinary albumin excretion (UAE) we studied the behavior of the UAE after 150 g of a meat protein meal and after a carbohydrate meal of equal caloric (1,370 kcal), water (1 liter) and sodium content (51 mEq). The mean creatinine clearance (Ccr) increased significantly after a protein load at the first (p less than 0.01) and second hour (p less than 0.05), while it did not change after the carbohydrate meal. The mean UAE increased significantly after the protein meal at the first (p less than 0.05) and second hour (p less than 0.05), while after the carbohydrate meal the mean values were increased at the first (p less than 0.05), second (p less than 0.05) and third hour (p less than 0.05). Furthermore, the mean values of UAE after the protein meal were significantly higher (p less than 0.05) than those found at the same time after the carbohydrate meal. Diuresis and natriuresis increased significantly after both meals. These findings show that the increased UAE after the protein meal may be due to a further increase in Ccr in the hyperfiltering remaining kidney, while the smaller increase in the UAE observed after the carbohydrate meal may be due to water load and increased urine flow, which impairs albumin tubular reabsorption. The prognostic importance of microalbuminuria after either meal is therefore uncertain.