Effect of dietary protein intake on albumin homeostasis in nephrotic patients

Animals with experimental renal disease maintained on diets restricted in protein develop less severe renal lesions and less proteinuria than do animals maintained on a normal or high protein diet. To determine whether restriction of dietary protein will reduce urinary albumin excretion in patients with established nephrosis and whether such dietary restriction will result in decreased albumin pools, we performed paired studies on nine nephrotic patients. They were fed sequential diets with a protein content of 1.6 and then 0.8 g/kg body wt, each for 2 weeks. Caloric intake remained constant at 35 Kcal/kg. In six patients the high protein diet was fed first; in three the order of dietary administration was reversed. Urinary albumin excretion was reduced on the low protein diet in all patients regardless of dietary order. Both the renal clearance of albumin and the fractional renal albumin clearance were reduced significantly on the low protein diet. The rate of albumin synthesis was greater on the high protein diet, but so was the rate of albuminuria. Despite the higher rate of albumin synthesis during the period of high protein intake, serum albumin concentration and plasma albumin mass were both less than during the period of low protein intake. Thus, dietary protein restriction in patients with established nephrosis results in decreased urinary albumin excretion in excess of any reduction in creatinine clearance. Total albumin mass is preserved and plasma albumin mass is actually increased during the period of dietary protein restriction. Protein restriction may be feasible in nephrotic patients.(ABSTRACT TRUNCATED AT 250 WORDS)