Renal handling of endogenous lysozyme in man
Pruzanski, W.; Wilson, D.R.
Journal of Laboratory and Clinical Medicine 90(1): 61-67
1977
ISSN/ISBN: 0022-2143 PMID: 267155 Document Number: 113490
The renal handling of lysozyme (lzm) was studied by estimation of the lzm level in arterial and renal venous blood samples taken simultaneously in patients with normal or mildly impaired renal function who were undergoing cardiac catheterization. Peripheral venous blood and urinary lzm and its clearance were also estimated in these patients and in patients with monocytic and myelomonocytic leukemia or with adult Fanconi syndrome. In 40 patients undergoing cardiac catheterization the mean arterial lzm concentration was 7.5 .+-. 0.3 .mu.g/ml (.+-.SEM ) and of renal vein lzm 6.9 .+-. 0.3 .mu.g/ml (SEM), with a mean extraction of 9% .+-. 2 (SEM). There was no detectable arteriovenous difference in 16 patients. Renal vein lzm was never higher than arterial lzm. The mean renal extraction rate of lzm, with normal renal plasma flow assumed, was 59 ml/min. Clearance of lzm (clzm) was very low, 0.04 .+-. 0.01 ml/min (SEM), indicating nearly complete tubular reabsorption and creatinine clearance (ccr) was 74 .+-. 5 ml/min (SEM), with clzm/ccr of 0.05% .+-. 0.01 (SEM). Even in the presence of impaired proximal tubular function (adult Fanconi syndrome) clzm was only 2-14% of ccr. In 43 patients with monocytic or myelomonocytic leukemia the urinary excretion of lzm increased markedly when the serum level exceeded 25-30 .mu.g/ml; the filtered load was 3-5 times normal and continued to increase with suggestive evidence of saturation of tubular reabsorption at filtered loads 6-12 times normal. Under normal conditions, the renal extraction rate of lzm was sufficient to account for lzm catabolism, although the absence of detectable extraction in some subjects indicates that the metabolic rate may at times be very low. Renal handling of endogenous lzm in man was characterized by a low-threshold high-capacity tubular reabsorption system.