Carol J. Ellis

Comparison of serum amylase pancreatic isoamylase and lipase in patients with hyperamylasemia

We compared results of measurements of total serum amylase, pancreatic isoamylase, and lipase measurements in patients with hyperamylasemia. Serial measurements of these three enzyme levels in patients recovering from acute pancreatitis indicated that pancreatic isoamylase and lipase were elevated above normal to a greater extent and remained elevated much longer than did the total amylase. This finding indicates an appreciable sensitivity advantage of the pancreatic isoamylase and lipase over total amylase measurement during the recovery phase of pancreatitis. Comparison of pancreatic isoamylase and lipase levels in selected sera indicated a good correlation (r=0.84) between these two measurements in patients who did not have macroamylasemia. Lipase was normal in sera with amylase elevations due solely to salivary isoamylase. Thus, in nonmacroamylsemic sera, pancreatic isoamylase and lipase appear to be roughly interchangeable markers of the level of pancreatic enzymes in the blood. An advantage of the lipase assay is that this enzyme is normal in hyperamylasemia caused by macroamylasemia, whereas the inhibitor assay indicates that the pancreatic isoamylase is elevated. Development of automated assays for either pancreatic isoamylase or lipase should lead to the routine use of one of these assays in place of the present reliance on total amylase measurements in the diagnosis of pancreatitis.

Mechanism of Increased Renal Clearance of Amylase/Creatinine in Acute Pancreatitis

We investigated three possible causes of the increased ratio of amylase/creatinine clearance observed in acute pancreatitis. The presence of rapidly cleared isoamylase was excluded by studies of serum and urine, which demonstrated no anomalous isoamylases. In pancreatitis, the ratios (+/-1 S.E.M.) of both pancreatic isoamylase (9.2+/-0.6 per cent) and salivary isoamylase (8.6+/-1.6 per cent) were significantly (P less than 0.01) elevated over respective control values (2.4+/-0.2 and 1.8+/-0.2 per cent). Increased glomerular permeability to amylase was excluded by the demonstration of normal renal clearance of dextrans. We tested tubular reabsorption of protein by measuring the renal clearance of beta2-microglobulin, which is relatively freely filtered at the glomerulus and then avidly reabsorbed by the normal tubule. During acute pancreatitis the ratio of the renal clearance of beta2-microglobulin to that of creatinine was 1.22+/-0.52 per cent, an 80-fold increase over normal (0.015+/-0.002 per cent), with a rapid return toward normal during convalescence. Presumably, this reversible renal tubular defect also reduces amylase reabsorption and accounts for the elevated renal clearance of amylase/creatinine observed in acute pancreatitis.

A Rapid and Simple Assay to Determine if Macroamylase Is the Cause of Hyperamylasemia

Macromolecules are known to precipitate selectively in concentrated solutions of polyethylene glycol. This report describes the use of polyethylene glycol 6000 to distinguish macroamylase from normal-sized serum amylase. Preliminary studies indicated that a PEG concentration of 12% and a 10-min incubation at 37 degrees C separated normal serum amylase from macroamylase. Using these conditions, study of 18 macroamylase-containing sera showed precipitation of at least 73% of the amylase activity. In contrast, in 46 normal sera and 16 hyperamylasemic (but not macroamylasemic) sera, less than 52% of the amylase activity was precipitated by polyethylene glycol. This test provides a rapid, simple, and accurate means of determining if macroamylasemia is the cause of hyperamylasemia.

Extrapancreatic Origin of Chronic Unexplained Hyperamylasemia

ELEVATED serum amylase activity in a patient with abdominal pain usually indicates pancreatitis. Ordinarily, the amylase level returns to normal within several days; however, a small percentage of ...

Evaluation of an inhibitor assay to determine serum isoamylase distribution

We tested a technique to distinguish salivary from pancreatic isoamylase using a wheat protein which inhibits salivary isoamylase. The inhibitor technique accurately reflected the preponderance of pancreatic or salivary isoamylase in sera which had been “spiked” with human pancreatic or salivary isoamylase. Comparison of the results of either cellulose acetate electrophoresis or isoelectric focusing showed an excellent correlation (r=0.99) in 43 hyperamylasemic sera which did not contain macroamylase. Normal values (1sd) of total serum amylase activity and the upper limit of normal for serum pancreatic isoamylase was 166 IU/liter. The inhibitor assay provides a simple and accurate means of differentiating salivary from pancreatic hyperamylasemia.

Influence of Amylase Assay Technique on Renal Clearance of Amylase-Creatinine Ratio

The influence of amylase assay technique on the renal amylase/creatinine clearance measurement was determined by analysis of serum and urine specimens obtained from 10 normal subjects. CAm/CCr averaged 2.19 +/- 0.18% with a saccharogenic technique, 1.52 +/- 0.2% with an iodometric technique, and 0.80 +/- 0.08% with a chromogenic technique. Each of these values differed significantly (P less than 0.05) from the other two. Recovery studies were carried out by adding partially purified human salivary or pancreatic amylase to human newborn serum or urine (which contain minimal endogenous amylase). Equal amylase activity was recovered from serum and urine by the saccharogenic technique whereas recovery from urine was less than 50% of that from serum using the iodometric and chromogenic techniques. The accuracy of the chromogenic technique is markedly improved by the addition of albumin to the urine assay system. Although it appears that only the saccharogenic method provides an accurate estimate of CAm/CCr, each assay technique distinguished the elevated CAm/CCr of patients with pancreatitis from the normal range established for that technique. Accurate clinical interpretation of CAm/CCr measurment requires knowledge of the amylase assay technique used.

Influence of method of alveolar air collection on results of breath tests.

The influence of the method alveolar aircollection on measurements of trace gas concentrationhas received little attention. We measured theconcentrations of H2, CH4, CO, andCO2 in sequential fractions of alveolar air collected with and withoutbreath-holding. Without breath-holding, theconcentration of these gases increased appreciably asincreasing quantities of alveolar air were expelled.Twenty seconds of breath-holding markedly reduced thisnonhomogeneity of alveolar air. Prediction of theexcretion rate of trace gases from measurements of theirconcentration relative to CO and literature values for resting CO2 excretion underestimatedthe true excretion rate. We conclude that breath-holdingprior to sample collection enhances the reproducibilityof trace gas measurements. When calculating the rate of excretion of trace gases, the use ofliterature values for resting ventilation orCO2 excretion may result in appreciableunderestimations of the true rate.

Carbon monoxide generation from hydrocarbons at ambient and physiological temperature: a sensitive indicator of oxidant damage?

This paper shows that a variety of carbon-containing materials (wool, cotton, wood, paper, latex, Tygon) release CO during incubation at ambient temperature. This CO production was enhanced by aerobic versus anaerobic incubation, increasing temperature, and exposure to fluorescent light. CO production from glucose solutions was enhanced by alkaline pH or prior boiling or autoclaving and reduced by the presence of superoxide dismutase or catalase. We conclude that a variety of materials are constantly undergoing oxidation at ambient or physiological temperature as evidenced by the release of CO. Measurements of this CO production could provide a simple, rapid and sensitive means of assessing oxidative damage.

Storage of breath samples for H2 analyses

Breath hydrogen tests are limited by leak of gases from breath samples from standard glass or plastic syringes. These losses may be substantial when these samples are stored for long periods of time. We describe a simple manipulation involving the use of a mineral oil or water seal at the end of the syringe barrel that markedly reduces the leakage of H2 and other gases to negligible levels.

Temperature dependence of macroamylase binding.

The presence of macroamylasemia can be suspected when a patient has low renal clearance of amylase relative to creatinine (Cam/Ccr). However, the Cam/Ccr is seldom reduced to the extent expected given the fraction of amylase that appears to be bound in the macroamylase complex by gel filtration studies at 3°C. Therefore, we tested the possibility that the binding of amylase in macroamylase complexes was temperature dependent and that binding at physiological temperatures might be less than at 3°C. Gel filtration of five macroamylase-containing sera was carried out at temperatures of 3°, 25°, 37°, 43°, and 49°C. Binding of amylase in the complex decreased as the temperature increased with virtually all amylase bound at 3°C and virtually no amylase bound at 49°C. The fraction of the amylase that bound at 37°C was approximately what would have been predicted from the Cam/Ccr of each of the five subjects. We conclude that amylase binding in macroamylase complexes is extremely temperature sensitive and appreciable changes in binding may occur over the physiological temperature range of 37–41°C.