抄録
Radioimmunoassay method for determination of retinol-binding protein (RBP), originally reported by Smith et al. and modified by Muto et al., was studied to measure the low level of the protein in urine without prior concentration process. For purification of labelled RBP, prepared by iodination using chloramine T method, affinity column chromatography of prealbumin coupled to Sepharose 4-B was successfully applied to. Double antibody technique was used and the method yielded reproducible results in the ranges of 5-50ng per assay.
In order to extend the results of the previous study, differentiation of the patterns of proteinuria was further studied by measuring urinary excretion of total protein, albumin and RBP. Four types of proteinuria (normal, glomerular, tubular and mixed glomerular-tubular proteinuria) were differentiated by the double logarithmic plot of albumin and RBP excretion in urine. Serial determinations of the pattern of proteinuria in the same patient were found to be useful for following the course of the disease and involvement of the site of lesion in the kidney.
In this experiment, the glomerular pattern was found in the cases of chronic nephritis, nephrotic syndrome and diabetic nephropathy; the tubular pattern mainly in the cases of “Itai-Itai” disease; the mixed pattern in uremic patients with diabetic nephropathy, multiple myeloma and other etiologies.
It was concluded that the measurement of low molecular weight protein as RBP together with albumin excretion in urine would be very important for the earl y detection of tubular dysfunction and the differentiation of proteinuric patterns.
