Histochemical and immunocytochemical characterizations of laminated bodies in the pancreas acinar lumen.

Combined adrenalectomy and castration cause numerous morphological alterations in the exocrine pancreas of the rat. Accumulation of laminated bodies (LB) in the acinar lumen is one of these alterations. A series of classical histological stains was applied to identify the components of these structures. A positive reaction was observed with periodic acid-Schiff, Congo red, and Alcian blue (pH 2.5). The first stain reacts with neutral and some acid mucosubstances and the second with amyloid, whereas the last one reacts with sulfated and nonsulfated acid mucosubstances. The LB also responded to Luxol fast blue, indicating the presence of lipids, an observation that is in agreement with the osmiophilic properties of these structures. A more specific identification of LB components was carried out with the immunocytochemical protein A-gold technique. Presence of gamma-glutamyltranspeptidase (gamma-GT) and GP2, two glycoproteins known to be secreted by the pancreas, was tested. The gamma-GT was associated with LB whereas GP2 was found in the lumen but not associated with these structures. Amylase was undetectable when LB occupied the lumen, suggesting that the process leading to production of LB also blocks secretory activity. To determine if diet influences LB accumulation in the pancreas acinar lumen, their frequency was compared in rats fed Purina Lab Chow or a lipid-free synthetic diet. A significant increase was observed in castrated-adrenalectomized rats fed the latter diet. This increase corresponded to a pronounced reduction in the number of zymogen granules (ZG) in the acinar cell. Our results show that LB are made of lipids, neutral mucosubstances, and nonsulfated acid mucosubstances, and that hormonal (steroids) and dietary factors (lipids) influence their accumulation.