Metabolism of bence jones proteins in non-myeloma patients with normal renal function

Non-secretory or low-secretory myeloma with intracellular kappa chains. Report of six cases and review of the literature

This report concerns six cases of multiple myeloma characterized by either no demonstrable monoclonal immunoglobulin in plasma or urine or by trace amounts (less than or equal to 0.1 g/l) of monoclonal kappa chains in the urine. In all cases there was an infiltration of the bone marrow by plasma cells containing kappa chains but no heavy chains. A retrospective analysis was made of 126 consecutive cases of Bence Jones myeloma. The number of kappa and lambda cases was approximately the same. All cases secreting less than or equal to 0.1 g light chains per 1 urine were of kappa type. This contrasts with a kappa/lambda ratio of 1.4-1.9 among reported series of M-components containing both heavy and light chains. A review of reported cases of non-secretory myeloma revealed a preserved capacity for Ig synthesis in the majority of cases and among these a preponderance of kappa chain producing clones. These observations might be explained by a higher tendency for kappa chain producing cells to mutate to low secretors or to cells producing abnormal light chains which are catabolized rapidly. The clinical data from our patients do not indicate a more pessimistic prognosis in non- or low-secretory myeloma, than in other cases of multiple myeloma.

Metabolism of complement factor D in renal failure

Factor D is an essential enzyme of the alternative pathway of complement. Its plasma concentration increases approximately tenfold in end-stage renal failure (ESRF). To analyze its metabolism in humans, we injected purified radiolabelled factor D into 5 healthy individuals and 12 patients with various renal diseases or renal failure. Fractional metabolic rates (FMR) and extravascular/intravascular distributions (EV/IV) were calculated using a compartmental model. The FMR was very rapid in normal individuals (mean 59.6%/hr; range 74.1 to 50.5), significantly diminished in the five patients with ESRF (5.7%/hr; 7.0 to 2.8; P less than 0.004), and correlated well with the creatinine clearance (r = 0.89; P less than 0.001). The extrarenal catabolic rate was not modified in renal failure. Despite a significant inverse correlation between plasma levels of factor D and creatinine clearance [r = 0.68; P less than 0.002], factor D levels were not a sensitive indicator of renal function because the synthesis rate (SR) varied widely from one individual to another (mean SR: 62.9 micrograms/kg/hr; 14.9 to 136.5). Factor D synthesis was not significantly altered by renal function, and did not correlate with C-reactive protein, suggesting that factor D is not an acute phase protein. The proportion of intact factor D elimination in the urine was increased in patients with tubular dysfunction (up to 15% compared to less than 0.2% in normal individuals) confirming that under normal circumstances factor D is filtered through the glomerulus and catabolized by tubular cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Nephrotoxicity of Bence Jones proteins in the rat: importance of protein isoelectric point

Bence Jones proteins (BJP) were isolated from the urine of 12 patients with multiple myeloma and various degrees of renal dysfunction. Proteins were characterized as to type (six type lambda and five type kappa), isoelectric point (pI), and secondary structure by circular dichroism (CD). Clinical renal function was more impaired with type-lambda proteins and with proteins of pI greater than 5.7. CD studies distinguished kappa from lambda proteins in most cases but did not correlate with nephrotoxicity. Protein dimer preparations were tested for nephrotoxicity in aciduric, hydropenic, female, Sprague Dawley rats by following renal function and morphology over 6 hours after injection i.p. of 300 mg of protein. Twelve rats of urine pH less than 5.5 injected with four BJP of pI less than 5.7 showed a mean rise in SUN of 5.3 mg/dl and in creatinine of 0.06 mg/dl, compared with a mean rise of 28.0 mg/dl (SUN) and 0.75 mg/dl (creatinine) in 21 rats injected with seven BJP of pI greater than 5.7 (P less than 0.01). Seven sodium-bicarbonate-fed rats of urine pH greater than 8 injected with a BJP of pI 6.2 showed mean rise in SUN of 1.8 mg/dl and in creatinine of 0.01 mg/dl, compared with 19.3 mg/dl (SUN) and 0.55 mg/dl (creatinine) in 7 aciduric rats injected with the same BJP (P = 0.009). Morphologic and immunohistologic studies showed distal cast formation in 9 rats with acute deterioration in renal function. It is concluded that BJP of pI greater than urine pH are acutely nephrotoxic in the rat by a mechanism that may involve a charge interaction in the distal nephron.

Retinol binding protein in serum and in urine of glomerular and tubular nephropathies

RBP behavior was studied in different kidney diseases. Serum RBP was increased in chronic renal diseases when the serum creatinine increased. RBP clearance and RBP clearance as a percentage of albumin clearance increased when GFR decreased; this is more evident in tubular kidney diseases. Urinary RBP loss as a percentage of urinary albumin loss increased especially in kidney diseases with persistent tubular lesions.

The renal handling of low molecular weight proteins. II. Disorders of serum protein catabolism in patients with tubular proteinuria, the nephrotic syndrome, or uremia

The present study was directed toward determining the role of the kidney in the metabolism of various classes of serum proteins and to define the urinary protein excretion patterns and the pathogenesis of disorders of protein metabolism in patients with proteinuria. To this end, the metabolic fates of a small protein, lambda-L chain (mol wt 44,000), and a protein of intermediate size, IgG (mol wt 160,000), were studied in controls and patients with renal disease. Controls metabolized 0.28%/hr of circulating IgG and 22.3%/hr of circulating lambda-L chain. All the IgG and 99% of the lambda-L chain was catabolized with the remaining lambda-L chain lost intact into the urine. The kidney was shown to be the major site of catabolism for small serum proteins. Three distinct disorders of protein metabolism were noted in patients with renal tubular disease and tubular proteinuria, glomerular disease (the nephrotic syndrome), and disease involving the entire nephrons (uremia), respectively. Patients with renal tubular disease had a 50-fold increase in the daily urinary excretion of 15-40,000 molecular weight proteins such as lysozyme and lambda-L chains. Serum IgG and lambda-L chain survivals were normal; however, the fraction of the over-all lambda-L chain metabolism accounted for by proteinuria was increased 40-fold whereas endogenous catabolism was correspondingly decreased. Thus, tubular proteinuria results from a failure of proximal tubular uptake and catabolism of small proteins that are normally filtered through the glomerulus. Patients with the nephrotic syndrome had a slight increase in lambda-L chain survival whereas IgG survival was decreased and the fraction of IgG lost in the urine was markedly increased. Here, abnormal glomerular permeability to proteins of intermediate size is the basic abnormality. Patients with uremia had a normal IgG survival but a four to 10-fold prolongation of lambda-L chain survival due to loss of entire nephrons, the major site of metabolism of these proteins. This results in an increase (up to 10-fold) in the serum concentration of lambda-L chain, lysozyme, and other small biologically active proteins, a phenomenon that may be of importance in causing some of the manifestations of the uremic syndrome.

Lysozyme turnover in man

Lysozyme turnover studies with (125)I-labeled human lysozyme were carried out on 22 patients, viz. nine control patients, seven nephrological patients with varying degrees of renal insufficiency, including three bilaterally nephrectomized patients, and six hematological patients with disturbed turnover of the neutrophilic granulocytes. It was found that plasma lysozyme has a rapid turnover with a fractional catabolic rate of 76%/hr of the plasma content. Lysozyme catabolism varied with the endogenous creatinine clearance; in addition however, extrarenal sites of catabolism were demonstrated since lysozyme could be broken down in the anephric patients, although only at a rate amounting to about 15% of the rate found in persons with intact kidneys. In the uremic patients the increased plasma lysozyme concentration was due to decreased rates of catabolism; in the hematological patients the increased plasma lysozyme level was due to increased rates of synthesis which supports the hypothesis that plasma lysozyme mainly stems from disintegrating neutrophilic granulocytes. Furthermore, it was shown that in the nonhematological patients examined, the rate of synthesis varied with the endogenous creatinine clearance.