Renal filtration and catabolism of complement XXXX .

@entity1 @entity644 @entity1985 @entity177 @entity563 @entity1011 @entity4434 @entity16678
Complement @entity16678 , a @entity563 protease participating in the formation of the C3 convertase of the alternative complement pathway, has the lowest molecular weight (23,750) and serum concentration of all complement proteins. In normal serum, D is the rate-limiting protease of the alternative pathway of complement activation. We report that the serum concentrations of D in 20 @entity1 with @entity177 (mean +/- S.D., 0.42 +/- 0.28 mg per deciliter) and in 16 @entity1 on long-term dialysis (1.53 +/- 0.39 mg per deciliter) were significantly higher (P less than 0.001) than in 22 healthy adults (0.18 +/- 0.04 mg per deciliter). In @entity177 the serum concentration of D correlated with that of @entity1011 (r = 0.75, P less than 0.001). The serum concentrations of D found in @entity1 with @entity177 reached and in some cases exceeded those at which the protease is no longer rate-limiting. Thus, enhanced activity of the alternative pathway of complement should be expected in @entity1 with @entity177 . Urinary D was undetectable (less than 0.2 micrograms per deciliter) in 17 normal adults and either undetectable or below the concentration expected from the degree of @entity644 in 10 @entity1 with @entity1985 . However, in a @entity1 with @entity4434 the urinary concentration of D (1.3 mg per deciliter) was an order of magnitude higher than the serum concentration, representing 0.5 per cent of the total protein. The urinary D in this @entity1 had normal hemolytic activity, antigenicity, and size. These results indicate that D is filtered through the glomerular membrane and is probably catabolized in the proximal renal tubules.
