Reference intervals for amylase isoenzymes in serum and plasma of infants and children

Measurement of pancreatic (P) and salivary-like (S) amylase isoenzyme activity in serum of adults is useful as an indirect indicator of pancreatic and salivary gland exocrine dysfunction. To extend the use of this assay to the pediatric population, we measured amylase isoenzymes in 546 serum and plasma samples and defined normal reference intervals for the P and S isoenzymes as a function of age in newborns, infants, and children. The mean activity of P isoenzyme in newborns is 3% of that of adults, begins to increase at seven to eight months, and reaches adult values by five years. The mean activity of S isoenzyme in serum is 32% of the adult mean at birth, begins to increase by three to four months, and reaches adult values by 19 months; children five to 12 years old have slightly higher values than adults. These changes with age underscore the importance of the use of age-matched reference intervals when serum amylase isoenzyme activities are measured as diagnostic indicators.     

Electrophoretic amylase fractionation as an aid in diagnosis of pancreatic disease.

Six alpha-amylase (EC 3.2.1.1) isoenzymes have been resolved electrophoretically on cellulose acetate membranes in a discontinuous buffer system. The fastest migrating isoenzymes are of salivary origin (S1, S2, S3), the slower ones of pancreatic origin (P1, P2, P3). We determined the amylase isoenzyme distribution in the sera of 240 subjects. A specific pancreatic isoenzyme (P3) was observed in all clinically diagnosed cases of acute or chronic pancreatitis as well as in 15 of 40 renal-transplant patients. Moreover, P3 isoenzyme activity declined during apparent recovery from pancreatitis. The P2 isoenzyme appeared in 95% of all specimens, P1 in only 2%. The pancreatic isoenzymes were preferentially excreted in the urine of both renal-transplant patients and normal individuals. The major salivary isoenzyme, S1, was observed in 95% of all serum and urine samples; however, the S2 and S3 appeared less consistently. Our method is simple and rapid, and quite applicable for use in clinical evaluation of patients with pancreatitis or with certain nonpancreatic dysfunctions.     

Enzyme immunoassay for human pancreatic amylase.

An enzyme immunoassay (EIA) for human pancreatic amylase has been developed for the detection of human serum amylase content. Our monoclonal antibody is highly specific for human pancreatic amylase; it cross reacted negligibly with the salivary isoenzyme. We developed a solid phase enzyme immunoassay for determination of pancreatic amylase in human serum with this antibody. The assay required 20 microL of serum and the standard curve was linear to at least 1000 ng/mL of pancreatic amylase. Inter- and intra-assay CVs were less than 10%. The results obtained by the EIA correlated well with those determined by the conventional electrophoretic method. In normal subjects, the mean concentration of serum pancreatic amylase determined by the EIA was found to be 92.3 +/- 26.1 ng/mL (mean +/- SD). The EIA we describe is useful for directly determining pancreatic amylase in human serum. Specifically distinguishing pancreatic from salivary amylase may have considerable clinical value.     

Pancreatic and salivary amylase determination using a short-chain chromogenic substrate (alpha-4-nitrophenyl-maltoheptaoside) and an amylase inhibitor

We describe a simple method to determine serum amylase isoenzyme activity with alpha-4-nitrophenyl-maltoheptaoside as substrate and the use of an amylase inhibitor. Day-to-day reproducibility (CV) was 2% for total amylase, 3-5% for pancreatic and salivary amylase; within-day precision was 1% for total amylase, 1-4% for pancreatic and salivary amylase. The concentrations of total, pancreatic and salivary amylase were determined in 169 sera obtained from healthy adults (82 men and 87 women). Total, pancreatic and salivary amylase concentrations in males were respectively 184, 105 and 66; in females 210, 97 and 92 U/l (mean). Our method is simple and rapid; our results agree well with those of other authors, who have used electrophoretic or blue starch methods.     

Rapid quantitative, specific measurement of pancreatic amylase in serum with use of a monoclonal antibody

In this rapid quantitative assay for pancreatic alpha-amylase (EC 3.2.1.1) in serum, we precipitate salivary amylases by 10-min incubation with monoclonal anti-salivary amylase antibody immobilized on particles of polyvinylidene fluoride. We then centrifuge the serum mixture and measure the pancreatic amylase activity remaining in the supernate by a kinetic method. The assay requires 50 microL of serum and the standard curve is linear to at least 1300 U of pancreatic amylase per liter of serum. CVs were 1.3% within-run, 6-8% day-to-day. Apparent analytical recovery of pancreatic amylase activity added to serum was 101% +/- 2%. Addition of purified salivary amylase, 356 U/L, to sera gave a value for apparent pancreatic amylase of less than 4 U/L, or 1% of the added salivary amylase activity. This assay correlated well with an electrophoretic method (slope, 0.97-0.99; intercept, 0.5 to -4 U/L; correlation coefficient, 0.946-0.990; and standard error of the estimate 3-5 U/L). Estimated normal reference intervals with maltotetraose as substrate were: total amylase, 39-118 U/L; pancreatic amylase, 11-50 U/L; and salivary amylase, 18-79 U/L.     

Assay of pancreatic amylase with use of monoclonal antibodies evaluated

To evaluate a new method for measuring pancreatic amylase in serum, in which the salivary isoenzyme is inhibited with a specific monoclonal antibody, we determined the activity of pancreatic and salivary amylase in sera from 103 healthy subjects and from 114 hospitalized patients having a wide range of total amylase activities. CVs for the proposed method ranged from 0.8% to 5.1% (within day) and from 2.3% to 6.6% (day to day). Results correlated well with those obtained by the wheat-germ inhibition method (r = 0.998) and by electrophoresis on cellulose acetate. Analytical-recovery studies confirmed the good specificity of the monoclonal antibody for salivary amylase (97%) and its low cross-reactivity (0.6%) toward pancreatic amylase. The assay procedure presents a wide range of linearity (141-1817 U/L) and can easily be adapted to an automated kinetic system. We found the proposed method suitable for routine determinations of pancreatic amylase.     

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.     

Electrophoretic pattern of amylase isoenzymes in serum and urine of normal persons.

We separated and measured amylase isoenzymes in the serum and urine of 3036 normal persons by electrophoresis on a thin layer of polyacrylamide gel. We wished to establish the normal pattern of these isoenzymes and to evaluate the usefulness of this method of electrophoresis in clinical diagnosis. Results for patients with hyper- or hypofunctioning pancreas and salivary glands suggested that essentially all the isoamylases in human serum and urine are derived from the salivary glands and the pancreas, and revealed that isoamylases of more than 98% of normal persons consisted of two major isoenzymes and two to three minor ones. Although these observations indicate that data on changes in the proportion of amylase activity of each isoenzyme can be useful in clinical medicine, the following points should be remembered: (a) quantitative differences in the isoenzyme pattern were observed, depending upon the condition of the samples; (b) because the proportion of isoamylase activity in serum of different normal persons differs, seriatim determination of amylase isoenzymes is necessary; and (c) because five different genetically controlled types of isoamylases were observed in normal persons, genetic investigations are also necessary.     

Survey of alpha-amylase activity and isoamylases in autopsy tissue

We quantified total amylase and its isoenzymes in 22 different human tissues obtained at autopsy. Isoenzymes were separated by use of wheat-germ inhibition (WI) and electrophoresis on cellulose acetate (CA) and agarose (AG). Mean (+/- SD) total activity was highest in salivary glands (parotid 1710 +/- 897 U/g, submandibular 605 +/- 354 U/g), and pancreas (258 +/- 137 U/g). All other tissues contained 100- to 1000-fold less amylase. As assessed with WI, pancreas, jejunum, liver, placenta, testis, skeletal muscle, and spleen contained more than 90% pancreatic isoamylase. Salivary glands and thyroid contained more than 90% salivary isoamylase. All other tissues contained a mixture of the two isoenzymes. CA and AG often produced different results. For both CA and AG the most common pancreatic isoforms were P2 and S1. Salivary gland homogenates demonstrated a band migrating in the P3 position on CA. We conclude that both types of amylase isoenzymes can be found in tissues other than salivary gland and pancreas, but that their low total amylase concentrations diminish their clinical importance.     

Catalytic concentrations of amylase isoenzymes: an assay with wheat-germ inhibitor and 4-nitrophenylmaltopentaoside plus 4-nitrophenylmaltohexaoside as substrate

We coupled a kinetic procedure to a selective inhibiting method for determining amylase isoenzymes in biological samples, using 4-nitrophenylmaltopentaoside plus 4-nitrophenylmaltohexaoside as substrate and a wheat-germ selective inhibitor with the Gilford S-III spectrophotometer. On plotting remaining amylase activities/total amylase activities (R/T) vs pancreatic amylase activities/salivary amylase activities (P/S) ratios, we found the curve to be linear for P/S ratios from 0.2 to 5. The inhibition rate of amylase inhibitor was constant in solutions having total amylase activities between 20 and (at least) 900 U/L. CVs were 3.1 to 7.1% for pancreatic amylase and 2.0 to 12.9% for salivary amylase in serum. Correlation with the Phadebas method was excellent (r = 0.99) for both pancreatic and salivary amylase. We also automated this procedure in an Hitachi 705 analyzer and correlated the results (r = 0.99) with those by our manual method.     

Hyperamylasemia after cardiac surgery in infants and children

Objective This study was conducted to clarify the incidence of hyperamylasemia after cardiac surgery in infants and children.Design and patients 186 infants and children operated on at Children's Hospital, Helsinki, during an 11-month period were enrolled in the study.Serum samples were taken before and on 3 consecutive days after cardiac surgery at the intensive care unit and before discharge from the hospital.Measurements We measured serum total amylase and serum pancreatic amylase with two different assays: (1) reduction of salivary amylase from total amylase activity and (2) measurement of mass concentration with monoclonal antibodies.Results Preoperative values for both total amylase and pancreatic isoenzymes were strongly agerelated. At least one of the three tests showed postoperative hyperamylasemia (>+2 SD above starting values of the age group and maximal value >3 times the individual starting value) in 64/186 (34%) patients. 22/186 (12%) patients had abnormal results in all assays. A more than tenfold rise in pancreatic amylase, suggesting pancreatitis, was found in 14 patients (8%).Mortality was 21% in this subgroup, but 5% in the rest of the patients. Hyperamylasemia was more common after 1 year of age, and after open-heart surgery, especially homograft implantation or cardiac transplantation.Conclusions Hyperamylasemia is a common finding after cardiac surgery in pediatric patients. Amylase isoenzyme measurements are needed for clinical decision making. Age-group-related reference values are mandatory for the right interpretation of amylase values.This work done at Children's Hospital, Helsinki, Finland     

Three methods compared for determination of pancreatic and salivary amylase activity in serum of cystic fibrosis patients

We evaluated three methods for serum amylase (EC 3.2.1.1) isoenzymes to determine whether they are interchangeable and to test their ability to discriminate between cystic fibrosis patients with and without pancreatic insufficiency. One method involved salivary amylase inhibitor (O), and two were polyacrylamide gel electrophoresis separations differing in method of detection--either direct zymogram (G) or gel slicing followed by activity estimates per slice (W). Results for percentage pancreatic amylase differed significantly. Reproducibility for percentage pancreatic amylase was high, moderate, and low (r = 0.95, 0.53, and 0.02) for methods G, O, and W, respectively; moderate (r = 0.60) among the three methods; and moderate between pairs. Therefore, this result for a subject must be considered relative to the method used in its determination. The clinical diagnosis of pancreatic insufficiency was verified by 77.8%, 83.3%, and 94.4% correct classification rates for methods O, W, and G, respectively. Evidently, method G is the most efficient and may be the method of choice for measuring serum amylase isoenzymes in cystic fibrosis.     

Total and pancreatic amylase measured with 2-chloro-4-nitrophenyl-4-O-beta-D-galactopyranosylmaltoside

BACKGROUND:: Many different methods have been used to assay amylase activity, using nitrophenylated oligosaccharides as substrate; however, the hydrolysis steps in these methods are complex. METHODS:: We developed a new continuously monitoring assay for amylase activity in biological fluids, using 2-chloro-4-nitrophenyl-4-O-beta-D-galactopyranosylmaltoside (GalG2CNP) as the substrate; this assay was used with anti-human salivary amylase monoclonal antibodies for specific determination of the pancreatic isoenzyme. Amylase converted GalG2CNP into beta-D-galactopyranosylmaltose and 2-chloro-4-nitrophenol, which was measured at 405 nm. RESULTS:: GalG2CNP was cleaved between 2-chloro-4-nitrophenol and beta-D-galactopyranosylmaltose and did not undergo transfer reactions. The within-assay CVs (n = 20) for total amylase (T-AMY) and pancreatic amylase (P-AMY) were 0.6-1.6% and 0.5-2.5%, respectively; and day-to-day CVs (n = 10) for T-AMY and P-AMY were 0.8-3.7% and 0.6-4.1%, respectively. T-AMY and P-AMY activities in serum or urine obtained by the proposed method correlated well with those determined by the 2-chloro-4-nitrophenyl 4-O-beta-D-galactopyranosyl-beta-maltotetraoside method or the modified IFCC method. CONCLUSIONS:: This novel assay for T-AMY and P-AMY measures both activities stoichiometrically, directly, and easily, and may be suitable for routine procedures.     

Simultaneous measurement of cholecystokinin-stimulated amylase release and cholecystokinin receptor binding in rat pancreatic acini.

In the past, isolated-dispersed pancreatic acini have been used to examine either cholecystokinin-stimulated amylase release or pancreatic acinar cholecystokinin receptors. We have developed and validated a method for simultaneous measurement of synthetic cholecystokinin octapeptide-stimulated (CCK8-stimulated) pancreatic amylase release and cholecystokinin receptors. After an 18-hour fast, rats were killed and their pancreatic acini isolated. Three-milliliter aliquots of acinar suspension were incubated for 60 minutes in N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-Ringer buffer containing graded doses of CCK8 and a constant amount (7 pmol/L) of iodine 125-labeled CCK8 (by the Bolton-Hunter method) ([125I]BH-CCK8). A 1 ml sample was removed from each flask for determination of amylase release, and the remaining 2 ml were used to determine cholecystokinin receptor capacities and affinities. The median effective dose for amylase release was 16 pmol/L, and release was maximal at 100 pmol/L CCK8 plus 7 pmol/L [125I]BH-CCK8, a dose that released 28% +/- 3% of total cellular amylase content. High affinity (equilibrium dissociation constant of high-affinity receptors = 58 +/- 8 pmol/L, receptor density of high-affinity receptors = 4 +/- 1 fmol/mg protein) and low affinity (equilibrium dissociation constant of low-affinity receptors = 7 +/- 2 nmol/L, receptor density of low-affinity receptors = 313 +/- 108 fmol/mg protein) cholecystokinin receptors were measured. The results demonstrate that CCK8-stimulated amylase release and cholecystokinin receptor binding in pancreatic acini can be measured concurrently and that the parameters of amylase release and cholecystokinin receptor binding are strikingly similar to those previously observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

A radioimmunosorbent technique for the assay of B- and C-types of carbonic anhydrase in human tissues.

A radioimmunosorbent technique for the assay of the human carbonic anhydrase isoenzymes HCA B and HCA C in tissue fluids was developed. The sensitivity of the method was 0.2 ng/ml and the precision was 5% in duplicate determinations for both enzymes. The presence in a tissue of up to 20 times higher concentrations of one isoenzyme will not interfere with the assay of the other. Haemolysates contained (mean +/- SE, n = 11) 12.1 +/- 0.52 and 1.5 +/- 0.06 mg enzyme/g Hb, and serum 0.63 +/- 0.12 and 0.2 +/- 0.02 microgram/ml of HCA B and HCA C, respectively. Pilot experiments indicated that the isoenzymes can be determined also in tissues, i.e. urine, saliva and cerebrospinal fluid, where catalytic methods previously have indicated absence of or only weak carbonic anhydrase activity. N-terminals of both enzymes were not antigenic.     

Rapid measurement of serum pancreatic amylase

A simple, rapid assay for the pancreatic isoenzyme of human serum amylase was developed. The assay utilized an immunoabsorbent prepared by coating latex beads with a monoclonal antibody specific for pancreatic amylase. Treatment of patient serum with immunoabsorbent removed pancreatic amylase, and measurement of residual amylase activity with standard total amylase methodology allowed estimation of the pancreatic amylase content. Extraction efficiency of pancreaticamylase was consistent at amylase concentrations up to 1,000 U/L (y = 0.97 × + 16.7 U/L; r = 0.9995). The assay was standardized with purified pancreatic amylase added to neonatal serum (low endogenous activity). A comparison of patient specimen results with the results of a standard technique (cellulose acetate electrophoresis) yielded an excellent correlation (immunoabsorption result = 0.96 electrophoresis result + 1.2 U/L; r = 0.987). Salivary amylase did not interfere with the assay until levels exceeded 1,000 U/L. Daily analysis of a frozen serum pool yielded a coefficient of variation of 9.2% at mean pancreatic amylase value of 54 U/L (±5 U/L). A normal range study found a strong influence of age, with pancreatic amylase levels increasing dramatically in the first 3 years of life, to stabilize at a range of 0–66 U/L thereafter. © 1994 Wiley-Liss, Inc.     

Macroamylasaemia after treatment with hydroxyethyl starch

After infusion of 500 ml of 6% hydroxyethyl starch into fifty-four patients an increase of serum amylase was observed which in fifty-one cases exceeded the upper limit of normal (190 U/l). In most cases serum amylase reached twice the basal value. Renal function influenced the duration of the increase in serum amylase, but not the maximum increase (201+/-15 U/l; mean+/-SEM). In patients with advanced renal failure (glomerular filtration rate (GFR) = 2-10 ml/min) serum amylase was still markedly elevated after 72 h (298+/-24 U/l; mean+/-SEM). In patients with normal renal function (GFR greater than 90 ml/min) serum amylase decreased to 183+/-40 U/l (mean+/-SEM) within 72 h without reaching basal values. After infusion of HES no changes were observed in serum lipase or in amylase or lipase activities in duodenal secretion. Amylase excretion in the urine decreased. The assumption of a macroamylasaemia caused by formation of an HES-amylase complex was confirmed by gel filtration. The elimination from plasma of this high molecular enzyme-substrate complex is slow and causes hyperamylasaemia. In no case was the macroamylasaemia associated with signs or symptoms. An awareness of this causal relationship seems to be important, to avoid the erroneous diagnosis of a pancreatic disease.     

Cancer, pancreatitis, and the detection of the isoenzymes of DNAase, RNAase and amylase.

Substrate films of starch, RNA, and DNA were used to identify the isoenzymes of amylase, RNAase, and DNAase found in human ductal pancreatic juice subjected to isoelectric focusing. The pancreatic secretions from 15 patients were shown to contain as many as four isoenzymes of RNAase; the two major forms had isoelectric points of 7.87 and 7.52, and the two minor forms, of 7.25 and 6.90. Six DNAase bands were detected; the major bands had pI values of 4.86 and 4.79, and sometimes appeared as one band. The minor bands had pI values of 5.08, 5.00, 4.68, and 4.58. Purified bovine DNAase I, analyzed similarly, showed four bands (5.29, 5.19, 5.04 and 4.96). Nine isoenzymes of alpha-amylase were observed in the secretions from 15 patients. The major alpha-amylase isoenzyme had a pI value of 6.84 in 14 patients and of 7.04 in 1 patient. Secondary bands were seen with pI values of 6.23, 6.53 and 6.69. Additional isoenzymes were found with pI values of 7.16, 6.39, 6.00 and 5.78. The amylase isoenzyme with a pI value of 6.39 was found in 7 of the 8 patients with a normal pancreas or carcinoma of the pancreas, and in only 1 of 7 patients with acute or chronic pancreatitis.     

Time-resolved immunofluorometric assay of human pancreatic isoamylase in serum, with use of two monoclonal antibodies

This new method for determining pancreatic isoamylase (EC 3.2.1.1) in serum involves two monoclonal antibodies: one immobilized in a microtitration well (the capture antibody), the other biotinylated. After the sample is incubated with the two antibodies, the captured immunocomplex is quantified by adding streptavidin labeled with a europium chelator and measuring the specific Eu3+ fluorescence in a time-resolved mode. Three assay protocols are proposed, involving incubation times of 90, 45, or 25 min. The assay has low (0.005%) cross-reactivity with the salivary isoenzyme. Analytical performance was satisfactory. Results correlate well with results obtained by measuring total amylase activity or by measuring pancreatic isoamylase activity after immunoinhibition. Unlike numerous current amylase assays, this method measures enzyme mass rather than enzyme activity. Potentially, this is a highly specific assay.     

Alpha-amylase determination with the Reflotron reagent carrier system: use of whole blood, plasma, and serum, and effect of isoenzymes

In the Reflotron Amylase dry-reagent carrier system (Boehringer Mannheim GmbH) a new substrate is used for determining total amylase (EC 3.2.1.1) activity:indolyl-alpha-D-maltoheptaoside. The procedure shows low imprecision (median CV less than 3.2%), and results for sera, plasma, and capillary and venous blood (y) correlate well with those of a conventional alpha-amylase method involving p-nitrophenyl (PNP)-maltoheptaoside substrate (x) (for 209 blood samples: y = 0.981x + 9.7; r = 0.994). Correlation was also excellent with a method involving maltotetraose as substrate (r = 0.987). Attachment of an indoxyl residue rather than a PNP group to the maltoheptaoside did not affect the substrate response to pancreatic or salivary isoenzyme activity. Therefore, the relative proportion of these isoenzymes did not affect the correlation between the Reflotron Amylase reagent carrier and the alpha-amylase PNP-maltoheptaoside method. With a reaction time of less than 3 min, this system is especially suitable for amylase determination in situations where a prompt result is required.