title: Enzymatic method for assaying calcium in serum and urine with porcine pancreatic alpha-amylase.
abstract: We developed a kinetic assay for calcium in serum and urine, based on the activation of porcine pancreatic alpha-amylase (EC 3.2.1.1) with 2-chloro-4-nitrophenyl-alpha-maltotrioside as substrate. The kinetic generation of 2-chloro-4-nitrophenol, monitored at 405 nm, was proportional to the concentration of calcium in serum and urine. The assay was developed and evaluated with the Cobas Bio centrifugal analyzer. The average within-run and between-day imprecision (CV) was 0.96/1.26% and 1.07/1.63%, respectively, for serum calcium and 1.50/2.54% and 1.70/2.64%, respectively, for urine calcium. Results of the proposed method (y) correlated well with those determined by atomic absorption spectrophotometry (x): y(serum) = 1.005x + 0.028 mmol/L (Sy/x = 0.058, r = 0.974, n = 50), and y(urine) = 1.017x-0.115 mmol/L Sy/x = 0.30, r = 0.981, n = 25). We also present data showing that the method is highly sensitive, rapid, relatively free of interference, and amenable to automation.
authors.affiliation: Department of Clinical Chemistry, National Cardiovascular Center, Osaka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kayamori
authors.forename: Y
authors.initials: Y
authors.lastname: Katayama
mesh_terms: D000818:Animals; D002118:Calcium / Q000097:blood* / Q000652:urine*; D002413:Cations, Divalent; D004789:Enzyme Activation; D006801:Humans; D007700:Kinetics; D010179:Pancreas / Q000201:enzymology*; D011786:Quality Control; D012680:Sensitivity and Specificity; D013054:Spectrophotometry, Atomic; D013552:Swine; D014312:Trisaccharides / Q000378:metabolism; D000516:alpha-Amylases / Q000378:metabolism*
chemical_list: D002413:Cations, Divalent; D014312:Trisaccharides; C057413:2-chloro-4-nitrophenylmaltotrioside; D000516:alpha-Amylases; D002118:Calcium