title: New evidences for the role of secretory ameloblasts in the removal of proline labelled proteins from young enamel as visualized by autoradiography.
abstract: Eight mice (M. musculus, albinus), two hours old, were sacrificed from 1 to 168 hours following the administration of a single dose of 1 microCi/g body weight of 3H-Thymidine. An other group of six mice received a single dose of 5 microCi/g body weight of 3H-Proline and the animals were killed from 20 min. to 120 h after the injection. The unfixed hemi-jaws containing one incisor tooth, were processed to obtain frozen cross serial sections. With time, as the tooth grows, the 3H-Thymidine labelled ameloblasts move away from the apical end of the incisor at a daily rate of 550 micrometer. By determining the silver grains content over ameloblasts and related enamel matrix in animals which received 3H-Proline, using serial sections separated from each other by 550 micrometers, it was shown that : 1) The silver grains concentration over secretory ameloblasts, which was maximum 20 min. after 3H-Proline administration, showed a decrease after 24 h and a new increase between 48 and 72 h and a further decrease at later time intervals ; 2) such second reactive peak was not observed in post-secretory ameloblasts; 3) the radioactive reaction over the enamel matrix after reaching a maximum 24 h after the injection, decreased at 48 h and another increase in radioactivity was detected at 96 h when the matrix moved incisally but was still related to secretory ameloblasts. The results were interpreted as indicative of the participation of the secretory ameloblasts in the removal of proline-containing protein, which can be considered either as one of the steps of enamel maturation, or also as evidence of a distinct process by which there would be a partial turnover of the organic matter in young enamel.
mesh_terms: D000565:Ameloblasts / Q000378:metabolism*; D000566:Amelogenesis; D000818:Animals; D001345:Autoradiography; D003743:Dental Enamel / Q000378:metabolism*; D003746:Dental Enamel Proteins / Q000378:metabolism*; D051379:Mice; D011392:Proline / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors; D014316:Tritium
chemical_list: D003746:Dental Enamel Proteins; D014316:Tritium; D011392:Proline; D013936:Thymidine