Abstract
Retinol - binding protein (RBP), a specific transport protein for vitamin A in human blood, has been shown to be excreted in large amounts in urine from patients with chronic cadmium poisoning and “Itai-Itai” disease.
In this report, biochemical abnormalities of serum constituents, renal function tests and urinary clearance of albumin, prealbumin and RBP were studied to elucidate the pathological mechanism for the increased RBP excretion.
Elevated level of serum creatinine and reduction of endogenous creatinine clearance were demonstrated in all of the cases with the disease. In about a half of them, retention of urea and elevation of alkaline phosphatase level in serum were observed. Serum levels of total protein, albumin and prealbumin were within the normal ranges with few exceptions. RBP level tended to be high in the cases of moderate nitrogen retention, and significant correlation of RBP and prealbumin levels was demonstrated in this experiment including the patients and their family members.
Clearance values of the 3 serum proteins of the patients were calculated in terms of μl/min. and compared with the average values in normal persons shown in parenthesis: albumin clearance 1.2 (0.14); prealbumin clearance 26 (0.1); RBP clearance 1260 (2.0). The major increase of the RBP clearance compared with that of the albumin clearance favors the grossly impaired reabsorption in renal tubules in the patients with the disease. However, a more complicated mechanism could be involved for the excretion of heterogenous forms of RBP and the increased prealbumin clearance.
