Localized Infusion of Tunicamycin in Rat Hemimandibles: Alteration of the Basal Lamina Associated with Maturation Stage AmeloblastsGiovanna Orsinia, Sylvia Zalzala, and Antonio Nanciaa Laboratory for the Study of Calcified Tissues and Biomaterials, Faculty of Dentistry, Université de Montréal, Montréal, Québec, Canada Correspondence to: Antonio Nanci, Université de Montréal, Faculty of Dentistry/Stomatology, PO Box 6128, Station Centre-Ville, Montréal, QC, Canada H3C 3J7. E-mail: Antonio.Nanci@umontreal.ca At the beginning of the maturation stage of amelogenesis, ameloblasts deposit a basal lamina (BL) at the interface between their apical surface and maturing enamel. This structure is rich in glycoconjugates and is proposed to exhibit adhesive and/or filtering functions. To clarify its role, we have applied a recently developed surgical window model to locally administer tunicamycin (TM), an antibiotic that interferes with N-glycosylation, in the rat hemimandible using an osmotic minipump. Male Wistar rats were infused with either TM or saline as a control. Lectingold cytochemistry was performed to reveal glycoconjugates in the BL. Immunogold labeling of enamel proteins and albumin was carried out to verify whether depletion of N-linked sugars in the BL affects the content and distribution of endogenous and exogenous proteins in the enamel layer. Under the influence of the drug, the BL became irregular and exhibited alterations in structural organization and composition. The number of Helix pomatia agglutinin binding sites was not significantly affected but their distribution was altered. The labeling density of wheat germ agglutinin over the BL was slightly reduced. Immunoreactivity for enamel proteins showed only a small decrease, but that of albumin, both between ameloblasts and within the enamel layer, increased significantly. No structural alterations were observed in the contralateral incisor and in other sampled tissues and organs. These results demonstrate that it is possible to achieve a localized administration of TM without systemic side effects and lend support to the proposal that the BL represents a specialized structure with filtering functions. (J Histochem Cytochem 49:165176, 2001) Key Words: osmotic minipump, tunicamycin, basal lamina, glycoconjugates, enamel proteins, colloidal gold, lectin cytochemistry, immunocytochemistry, incisor, rat
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