No abstract

An improved radiochemical rnethod is presented for the selective determination of phospholipase A 2 activity in human serum and ascites, using only commercially available reagents. The method can be applied to large quantities of samples. As Substrate we used l,2-dipalmitoyl-sn-glycero(3)phosphoiylcholine and phosphatidylcholine containing tritiated palmitic acid in position 2 (l-palmitoyl,2-[9,10-3 H]palmitoyl-snglycero(3)phosphorylcholine). The liberated fatty acids are extracted and radioactivity is detected in a liquid scintillation spectrometer.A preliminary reference ränge of human serum samples was established ranging up to 1.0 U/l. In sera of patients with acute pancreatitis we found activities up to 20 U/l. The correlation of phospholipase A 2 activity with that of other enzymes and with the severity and complications of acute pancreatitis was investigated. A possible relationship between phospholipase A 2 activities and pulmonary complications is discussed.

Serum from 48 patients with acute pancreatitis (21 with interstitial-edematous and 27 with necrotizing pancreatitis) was monitored for immunoreactive (IR) phospholipase A2 (PLA2) protein concentration and PLA catalytic activity. In both groups within 48 h after start of acute pancreatitis an up to tenfold increase of IR-PLA2 was demonstrable. Determination of IR-PLA2 revealed no differences between the groups. In contrast, determination of PLA catalytic activity allowed us to differentiate between patients with interstitial-edematous and necrotizing pancreatitis.

We investigated the effect of gabexate mesilate on the catalytic activity of phospholipase A2 in homogenized porcine pancreatic tissue. Gabexate mesilate is a potent inhibitor of serine proteases. There is no direct inhibition of phospholipase A2 catalytic activity in concentrations up to 6 mmol/l. Preincubation of homogenized pancreatic tissue with gabexate mesilate leads to a reduction of phospholipase A2 activity even in concentrations as low as 6 mumol/l. The activation of purified porcine prophospholipase A2 added to pancreatic tissue can be completely inhibited. Thus gabexate mesilate might influence the activation of phospholipase A2 administered in therapeutic concentrations in inflamed pancreatic tissue.

In a prospective clinical trial 85 patients with acute pancreatitis were analysed for serum total amylase, pancreatic amylase, pancreatic lipase, trypsin, elastase 1, and immunoreactive phospholipase A2 (IR-PLA2). The diagnostic sensitivity of serum IR-PLA2 was comparable to that of serum total amylase, pancreatic amylase, and trypsin. The specificity of IR-PLA2 is superior to that of serum total amylase determination due to the fact that the IR-PLA2 determination is based on an antibody against human pancreatic PLA2.