Lysozymuria in Patients with Proximal Tubular Dysfunction : The Relationship between Lysozyme and Sodium Reabsorption in the Proximal Tubule

Abstract

Activity of the low molecular weight protein lysozyme was measured by the lyso-plate method in the serum and urine of 25 normal adults and 51 patients suffering from various renal diseases, i.e. 22 primary glomerular, 19 primary interstitial, and 10 primary diseases. No correlation was found between serum and urinary lysozyme activities, although lysozymuria was present in all of the azotemic patients with serum lysozymeactivities greater than 90μg/ml, a threefold increase above normal serum levels. CLy fract was significantly higher in diseases, such as adult Fanconi syndrome, acute tubular necrosis, and transplanted kidney, than in glomerular diseases. In eight patients with primary tubular dysfunction, there were significantly correlated increases in CLy fract and CNa fract (r=0.931, CLyfract=1.21 CNafract-1.18). In a patient with unique ARF, who developed a period of oliguria followed by a massive diuresis- and saluresis during the diuretic phase, significant correlation was found about the increases in CLyfract and CNafract. In the rejection of a renal homotransplant, moreover, lysozymuria appeared with the elevated urinary Na/K ratios. The results of the present study suggest that the lysozyme reabsorption, which is essentially confined to the proximal tubule, may depend upon sodium reabsorption. Therefore, CLyfract may be useful as a clinical sign of proximal tubular dysfunction.