title: Evaluation of a direct prorenin assay making use of a monoclonal antibody directed against residues 32-39 of the prosegment.
abstract: BACKGROUND
  Prorenin is an early marker of microvascular complications in diabetes. However, it can only be measured indirectly (following its conversion to renin), with a renin immunoradiometric assay (IRMA). Unfortunately, treatment with a renin inhibitor interferes with this assay, because renin inhibitors induce a conformational change in prorenin, thereby allowing its detection as renin.
  
  
  METHODS
  We evaluated Molecular Innovation's new direct prorenin ELISA, which makes use of an antibody that recognizes an epitope near prorenin's putative cleavage site (R 43 L 44), thus no longer requiring prorenin activation. Plasma samples of 41 diabetic individuals treated with aliskiren (renin inhibitor) or irbesartan were tested. Semi-purified recombinant prorenin was used as standard, because the ELISA standard yielded approximately 10-fold lower values in the renin IRMA following its conversion to renin.
  
  
  RESULTS
  The ELISA detected prorenin levels that were identical to those determined by the IRMA in untreated and irbesartan-treated individuals. Yet, it yielded higher prorenin levels in aliskiren-treated individuals. Aliskiren, at levels reached in plasma during treatment, did not interfere with the ELISA, but allowed the detection of up to 20-30% of prorenin as renin in the IRMA, thereby resulting in a significant overestimation of renin and an underestimation of prorenin. The ELISA rendered results within 2 h and did not require a pretreatment period of several days to convert prorenin to renin.
  
  
  CONCLUSIONS
  The new direct assay allows rapid prorenin detection, is not hampered by aliskiren when used at clinically relevant doses, and might be used to identify diabetic patients developing retinopathy and/or nephropathy.
authors: Division of Pharmacology and Vascular Medicine, Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands.
authors: Manne
authors: M
authors: Krop
authors: Jeanette M G
authors: JM
authors: van Gool
authors: Duane
authors: D
authors: Day
authors: Norman K
authors: NK
authors: Hollenberg
authors: Alexander H
authors: AH
authors: Jan Danser
mesh_terms: D000368:Aged; D000911:Antibodies, Monoclonal / Q000737:chemistry*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D000939:Epitopes / Q000737:chemistry; D005260:Female; D006801:Humans; D015592:Immunoradiometric Assay / Q000379:methods; D007674:Kidney Diseases / Q000473:pathology; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D017434:Protein Structure, Tertiary; D012083:Renin / Q000097:blood* / Q000737:chemistry; D013997:Time Factors
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D012083:Renin