New evidences for the role of secretory ameloblasts in the removal of proline labelled proteins from young enamel as visualized by autoradiography.
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.
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
D003746:Dental Enamel Proteins; D014316:Tritium; D011392:Proline; D013936:Thymidine