Plasma kinetics of complement component C4: comparison of three models
Plasma C4 kinetics were studied in members of a kindred with hereditary incomplete C4 deficiency and in control subjects. Test subjects received iodine /sup 125/-labeled C4 intravenously, and plasma disappearance curves for 125I-C4 were plotted. By nonlinear least-squares analysis, we fit two-, three-, and four-exponential models of plasma disappearance to the plasma curves of each subject. Goodness of fit was significantly better for all subjects with the three-exponential versus the two-exponential model (p less than 0.0005). No further improvement in curve fit was accomplished by using a four-exponential model (p greater than 0.5). Metabolic rates and extravascular/plasma ratios calculated from the two- and three-exponential models were significantly different. As judged by extravascular/plasma ratio, the two-exponential model underestimated the amount of extravascular C4. Furthermore, the two-exponential model significantly over-estimated catabolic and synthetic rates. Hence, our results show that C4 kinetics are not optimally described by a conventional, two-exponential model. A possible explanation for our findings is that in previous studies of C4 metabolism, the analysis of plasma radioactivity disappearance curves was done by inspection, whereas we used least-squares analysis, a method that determines the number of exponentials with greater reliability.
- Research Organization:
- Case Western Reserve Univ., Cleveland, OH (USA)
- OSTI ID:
- 6270928
- Journal Information:
- J. Lab. Clin. Med.; (United States), Vol. 113:2
- Country of Publication:
- United States
- Language:
- English
Similar Records
In vivo behavior of human radioiodinated antithrombin III: distribution among three physiologic pools
Purified radiolabeled antithrombin III metabolism in three families with hereditary AT III deficiency: application of a three-compartment model
Related Subjects
COMPLEMENT
METABOLISM
BIOCHEMICAL REACTION KINETICS
COMPARATIVE EVALUATIONS
IODINE 125
LEAST SQUARE FIT
MATHEMATICAL MODELS
TRACER TECHNIQUES
BETA DECAY RADIOISOTOPES
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAXIMUM-LIKELIHOOD FIT
NUCLEI
NUMERICAL SOLUTION
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PROTEINS
RADIOISOTOPES
REACTION KINETICS
550501* - Metabolism- Tracer Techniques