title: An immunocytochemical study of the routes of secretion of collagen and phosphophoryn from odontoblasts into dentin.
abstract: Polyclonal antibodies to rat incisor phosphophoryns and to the amino-telopeptide of the alpha1 (I)-chain of type I collagen were used to follow the pathways of movement of collagen I (COL1) and phosphophoryns (PP) from synthesis in the odontoblast to secretion into the mineralized dentin. The antibodies were detected at the transmission electron microscopic level by their reaction with Protein A-colloidal gold conjugates. Special care was given in specimen preparation to retention of maximal antigenicity during fixation while maintaining cellular and extracellular ultrastructure at the mineralization front (MF) in nondemineralized sections. Intracellularly, COL1 and PP were detected within the endoplasmic reticulum (ER), the Golgi (G) and secretory granules (SG). However, as determined by double-immunolabeling with different size gold particles the COL1 and PP were not found together within the same ER, G or SG compartments. PP was localized within the tubular ER, round-shaped transitional vesicles, the Golgi and in narrow asymmetric SG. These asymmetric SG were found in abundance in the odontoblastic process. PP secretion from these vesicles was near the MF at the predentin-dentin boundary. COL1 was localized within rosette form ER compartments, the Golgi and in large, distinctive SG. COL1 was deposited at the cell-predentin boundary. No COL1 SG were seen within the odontoblastic process near the MF. In the region of the MF, prior to mineralization, the PP was localized along the surfaces of the COL1 fibrils of the predentin. The mineral phase etched surfaces revealed both COL1- and abundant mineral-associated PP. These data support the hypotheses that, in dentin, the interaction between COL1 and PP may initiate crystal nucleation and that additional interactions between PP and the growing crystals may modulate the crystal growth pattern and crystal size.
authors.affiliation: Northwestern University, Division of Oral Biology, Chicago, IL 60611, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Rabie
authors.forename: A
authors.initials: A
authors.lastname: Veis
mesh_terms: D000818:Animals; D000918:Antibody Specificity / Q000276:immunology; D002451:Cell Compartmentation / Q000502:physiology; D003094:Collagen / Q000378:metabolism*; D024042:Collagen Type I / Q000378:metabolism; D000090602:Collagen Type I, alpha 1 Chain; D003804:Dentin / Q000254:growth & development* / Q000378:metabolism / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D007150:Immunohistochemistry; D008297:Male; D046529:Microscopy, Electron, Transmission; D009804:Odontoblasts / Q000378:metabolism* / Q000648:ultrastructure; D010750:Phosphoproteins / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D022142:Secretory Vesicles / Q000378:metabolism / Q000648:ultrastructure; D014074:Tooth Calcification / Q000502:physiology
chemical_list: D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain; D010750:Phosphoproteins; C017630:phosphophoryn; D003094:Collagen