Automated measurement of amylase isoenzymes with 4-nitrophenyl-maltoheptaoside as substrate and use of a selective amylase inhibitor.

We automated a kinetic procedure for determining amylase isoenzymes in serum and urine samples. We used 4-nitro-phenylmaltoheptaoside as substrate and a selective amylase inhibitor with the Abbott-VP bichromatic system. By use of the maximum differences between pancreatic (P) and salivary (S) amylase activities remaining after inhibition by the selective inhibitor and by use of the linear range, a one-point standard method for calibration is proposed for determining amylase activities between about 50 and 1500 U/L when the P/S ratio exceeds 0.2. Results correlated well with those by electrophoresis and the Phadebas method (r = 0.99 for both pancreatic and salivary amylase). Reproducibilities (CVs) were 1.5% to 5.5% for pancreatic amylase and 1.4% to 3.3% for salivary amylase in serum, 0.8% to 2.0% for pancreatic amylase and 0.8% to 2.3% for salivary amylase in urine.