S. Lloret et Jj. Moreno, EDEMA FORMATION AND DEGRANULATION OF MAST-CELLS BY PHOSPHOLIPASE-A(2)PURIFIED FROM PORCINE PANCREAS AND SNAKE-VENOMS, Toxicon, 31(8), 1993, pp. 949-956
Phospholipase A2 is ubiquitous in nature, with the highest concentrati
ons occurring in pancreatic juice and in the venom of snakes. Local oe
dema formation is a common feature of the effects caused by snakebite,
and indicates an increase in vascular permeability that could be prod
uced by lipid mediators such as lysophospholipids, eicosanoids or PAF
release by the enzymatic activity of PLA2. Desalted porcine pancreatic
PLA2 exhibited strong oedema-inducing activity in a similar form to P
LA2 venom from Naja naja or Crotalus durissus terrificus. Furthermore,
all three PLA2s caused the release of histamine from rat peritoneal m
ast cells. However, non-desalted pancreatic PLA2 that was presented as
an ammonium sulphate suspension (3.2 M) had no proinflammatory activi
ty and clearly did not release histamine in vitro. When the enzymatic
activity of PLA2 on mast cell membranes prelabelled with [H-3] arachid
onic acid was determined, a relationship between the enzymatic activit
y and mast cell degranulation and the minimum oedema dose was observed
. However, non-desalted porcine pancreatic PLA2 had the same enzymatic
activity as the desalted enzyme but had little proinflammatory activi
ty. This may be due to decreased histamine secretion caused by the pre
sence of ammonium sulphate. Our study supports the idea that the proin
flammatory activity of extracellular phospholipases could depend on th
eir ability to cause mast cell degranulation. Moreover, the biological
effects of PLA2 are correlated with the specific activities of the en
zymes.