Comparative radioautographic study of the effects of L-azetidine-2-carboxylic acid on matrix secretion and golgi of the mouse incisor

Abstract

The effect of a proline analog, L-azetidine-2-carboxylic acid (LACA), on protein matrix secretion by odontoblasts and ameloblasts was compared by light and electron microscopic radioautography after injection of 3H-glycine in young mice. LACA inhibited the secretion of dentin matrix with consequent accumulation of 3H-glycine labeled procollagen in the cisternae of the rough endoplasmic reticulum. In contrast, LACA had no apparent effect on ameloblasts as enamel matrix continued to be packaged in the Golgi apparatus and secreted from Tomes' process within 30 min after injection of the radioprecursor. Electron microscopy revealed that LACA did not cause any change in ameloblast ultrastructure but produced a marked alteration of the odontoblast Golgi complex. All odontoblast Golgi saccules and collagen secretion granules disappeared within 2 h after LACA administration. Odontoblast Golgi cisternae, however, appeared not to be affected. These observations confirm previous studies conducted in this laboratory showing that Golgi saccules in collagen-secreting cells are the initial staging areas for the formation of secretory granules. These results also indicate that a close correlation exists between form and function in the Golgi apparatus of collagen-secreting cells.

Effects of L‐azetidine‐2‐carboxylic acid on matrix secretion and Golgi structure in fibroblasts and osteoblasts of the mouse

“…Quantitative analysis of silver grains in light microscopic radioautographs of 1-pm sections showed a pattern of 3H-glycine utilization in LACA-treated fibroblasts and osteoblasts similar to that observed in previous studies of collagen secretion in LACA-treated odontoblasts (Cho and Garant. 1984).…”

“…We have already shown that the structure of the Golgi apparatus of odontoblasts (collagen secretor) is affected by LACA administration while that of ameloblasts (noncollagenous protein secretor) remains unchanged (Cho and Garant, 1984). To further confirm the effect of LACA on the structure of the Golgi apparatus of other collagensecreting cells, we conducted a n electron microscopic and radioautographic study of collagen secretion in LACA-treated fibroblasts and osteoblasts.…”

“…Substitution of LACA for L-proline at a concentration of as little as four residues per alpha chain leads to inhibition of helix formation (Lane et al, 1971;Uitto and Prockop, 1974;Uitto et al, 1975). Failure to form the alpha helical configuration prevents the procollagen polypeptides from exiting the rough endoplasmic reticulum (Uitto et al, 1975).We have already shown that the structure of the Golgi apparatus of odontoblasts (collagen secretor) is affected by LACA administration while that of ameloblasts (noncollagenous protein secretor) remains unchanged (Cho and Garant, 1984). To further confirm the effect of LACA on the structure of the Golgi apparatus of other collagensecreting cells, we conducted a n electron microscopic and radioautographic study of collagen secretion in LACA-treated fibroblasts and osteoblasts.…”

Radioautographic analysis of 3H‐fucose utilization by fibroblasts of the periodontal ligament

“…However, unlike in collagen secretion where the 3H-proline labelled precursors accumulate relatively close to the cell surface, the 3H-fucose labelled glycoproteins appear to spread more rapidly from the secretory pole of the cell. It is of interest that 3H-fucose labelled glycoproteins secreted by odontoblasts appear to migrate to the mineralization front within 4 hours while 3H-proline labelled collagen requires approximately one full day to reach the same site (Weinstock et al 1972, Cho & Garant 1984.…”

Ultrastructural Observations on the Intraodontoblastic Collagen Fibrils of the Mouse Tooth Germs

“…1972: Wein stock and Leblond. 1974: Cho and Garant. 1984, fibro blasts or odontoblasts form secretory granules that contain collagenous fibrillar material with various banding periods.…”