Early events of secretory granule formation in the rat parotid acinar cell under the influence of isoproterenol. An ultrastructural and lectin cytochemical study.
The events involved in the maturation process of acinar secretory granules of rat parotid gland were investigated ultrastructurally and cytochemically by using a battery of four lectins [Triticum vulgaris agglutinin (WGA), Ulex europaeus agglutinin I (UEA-I), Glycine max agglutinin (SBA), Arachys hypogaea agglutinin (PNA)]. In order to facilitate the study, parotid glands were chronically stimulated with isoproterenol to induce secretion. Specimens were embedded in the Lowicryl K4M resin. The trans-Golgi network (TGN) derived secretory granules, which we refer to as immature secretory granules, were found to be intermediate structures in the biogenesis process of the secretory granules in the rat parotid acinar cell. These early structures do not seem to be the immediate precursor of the mature secretory granules: in fact, a subsequent interaction process between these early immature granule forms and TGN elements seems to occur, leading, finally, to the mature granules. These findings could explain the origin of the polymorphic subpopulations of the secretory granules in the normal acinar cells of the rat parotid gland. The lectin staining patterns were characteristic of each lectin. Immature and mature secretory granules were labelled with WGA, SBA, PNA, and lightly with UEA-I. Cis and intermediate cisternae of the Golgi apparatus were labelled with WGA, and trans cisternae with WGA and SBA.
D'Amico
F
F
Centro di Microscopia Elettronica di Medicina, University of Catania, Italy. f.damico@mbox.unict.it
Skarmoutsou
E
E
Imbesi
R M
RM
Sanfilippo
S
S
D000116:Acetylgalactosamine / Q000378:metabolism; D000117:Acetylglucosamine / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D005643:Fucose / Q000378:metabolism; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D007545:Isoproterenol / Q000494:pharmacology*; D037102:Lectins / Q000378:metabolism; D008297:Male; D019158:N-Acetylneuraminic Acid / Q000378:metabolism; D010306:Parotid Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D019887:Peanut Agglutinin / Q000378:metabolism; D037121:Plant Lectins; D051381:Rats; D017208:Rats, Wistar; D022142:Secretory Vesicles / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D030262:Soybean Proteins; D014909:Wheat Germ Agglutinins / Q000378:metabolism; D010835:Phytohemagglutinins
D000116:Acetylgalactosamine; D000117:Acetylglucosamine; D000318:Adrenergic beta-Agonists; D005643:Fucose; D007545:Isoproterenol; D037102:Lectins; D019158:N-Acetylneuraminic Acid; D019887:Peanut Agglutinin; D037121:Plant Lectins; D030262:Soybean Proteins; D014909:Wheat Germ Agglutinins; C036850:Ulex europaeus lectins; C028824:soybean lectin; D010835:Phytohemagglutinins