Presence and ontogeny of intestinal and pancreatic phospholipase A2-like proteins in the Red Sea bream,Pagrus major. An immunocytochemical study

Abstract

We have studied the location and the ontogeny of the digestive enzyme, phospholipase A2 (PLA2) immunohistochemically in the adult and larvae/juvenile of the red sea breamPagrus major by using an antiserum against theNaja naja venom PLA2. The antiserum reacts with at least one enzyme among the PLA2s purified from the fish hepatopancreas or intestine. Although the reactivities were comparatively low, it labelled zymogen granules of the pancreatic acinar cells and secretory materials of certain epithelial cells in the depths of epithelial crypts in the pyloric caeca of the adult. The immunoreactivities of PLA2s were investigated in the viscera of larvae and juveniles of the 0 to 85(th) day after hatch. In the larvae of the 13(th) day, accumulation of PLA2-positive zymogen granules in the pancreatic acinar cells were first recognized by the immunostaining. The intensity of the labelling subsequently became stronger and dramatically increased between the 20(th) and 30(th) day. This increase appeared to be one of the physiological changes associated with the transition to a new benthic life as juveniles. Lack of PLA2 in the pancreas before the 13(th) day may suggest the possibility that larvae utilized exogenous PLA2, inherent in their prey, to digest the phospholipids. On the other hand, no reactivity was found in the intestine until the 85(th) day.