Quantification of carbamylated LDL in human sera by a new sandwich ELISA.
BACKGROUND
We previously suggested that increased carbamylated LDL (cLDL), a product of nonenzymatic modification of LDL in human serum by urea-derived cyanate, may cause cardiovascular complications in patients with chronic renal insufficiency. An assay for precise measurement of cLDL in serum was not previously available.


METHODS
Polyclonal antibodies against human cLDL and nonmodified, native LDL (nLDL) were raised in rabbits and extensively purified by affinity chromatography. New sandwich ELISAs to measure cLDL and nLDL with use of these antibodies were developed. Serum concentrations of cLDL and nLDL were measured by the sandwich ELISAs in 41 patients with end-stage renal disease (ESRD) and 40 healthy controls.


RESULTS
Both assays showed satisfactory reproducibility, linearity, and recovery. The assays could detect 2.7 mg/L cLDL with a linear detection range of 5-1000 mg/L and 5 mg/L nLDL with a linear detection range of 50-1000 mg/L. These measurements showed that patients with ESRD have significantly increased serum cLDL [281.5 (46.9) mg/L compared with 86.1 (29.7) mg/L in a control group; P <0.001]. There was no significant difference in nLDL concentrations between the groups.


CONCLUSIONS
These assays are a potentially valuable tool for cardiovascular research in renal patients and healthy individuals. The cLDL concentration appears to be the highest among all previously described modified LDL isoforms in both controls and ESRD patients.
Apostolov
Eugene O
EO
Division of Nephrology, Department of Internal Medicine, University of Arkansas for Medical Sciences Little Rock, AR 72205, USA.
Shah
Sudhir V
SV
Ok
Ercan
E
Basnakian
Alexei G
AG
D000328:Adult; D000818:Animals; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000175:diagnosis / Q000628:therapy; D008077:Lipoproteins, LDL / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011817:Rabbits; D006435:Renal Dialysis; D012680:Sensitivity and Specificity
D008077:Lipoproteins, LDL; C039916:carbamyl-LDL