Resistance to the effect of phospholipase A₂ of the biliary phospholipids during incubation of bile

Mixtures of fresh bile of the rat and of isolated hepatic phospholipids (one or the other of these components having been labeled with 3 H oleic acid) were incubated either with heated rat pancreatic juice, at 37 C during periods of 1 and 3 hr, or with snake venom, at 25 C during periods of 17 and 36 hr, as sources of phospholipase A 2 . After incubation, tritiated free oleic acid was measured since this acid was in the 2 position of both phospholipidic substrates. With heated pancreatic juice, no significant enzymatic hydrolysis of the bile phospholipids occured, but isolated hepatic phospholipids were readily attacked. With snake venom, the whole isolated hepatic phospholipids were very strongly hydrolyzed while biliary phospholipids were hydrolyzed to a much lesser extent.