Radioautography of rat incisor dentin as a continuous record of the incorporation of a single dose of /sup 3/H-labeled proline and tyrosine
After injection of labeled precursors such as /sup 3/H-proline or /sup 3/H-tyrosine into rats, the incisor dentin contains a continuous and stable record of precursor incorporation into labeled proteins. This record was visualized and quantitated with radioautography in order to evaluate the quantitative changes in enamel where newly secreted proteins randomize with older proteins and both are eventually lost. Up to 4 hours after injection, the pulse-dose was incorporated as a highly labeled band of predentin. The band was entirely within calcified dentin at 2 days and was further removed from new predentin by 4 and 8 days. Dentin which formed proximal to the heavily labeled band contained an amount of radioactivity reflecting the level of labeled precursor available at that time. A standardizing factor for experimental error was obtained by quantitating the reaction in the heavily labeled band, and a post-pulse incorporation factor was determined from the amount of radioactivity added per day as weakly labeled dentin. The variation within the heavily labeled band was assumed to reflect experimental error. The number of grains in the bands were averaged from 4 hours to 8 days to give the standardizing factor. This was multiplied by the ratio of enamel to dentin counts in the same section to obtain a corrected enamel count. With proline it amounted to 5% increase per day from 1 to 4 days and 2.5% per day from 4 to 8 days after injection. In addition, with /sup 3/H-proline the incorporation into predentin increased from 30 minutes to 4 hours. With tyrosine, the counts increased from 30 minutes to 1 hour, but decreased by nearly one third from 1 to 4 hours. This was interpreted as a loss of short-lived matrix proteins including procollagen peptides produced during conversion from procollagen to tropocollagen in the predentin.
- Research Organization:
- Department of Anatomy, McGill University, Montreal, Quebec, Canada
- OSTI ID:
- 6656254
- Journal Information:
- Am. J. Anat.; (United States), Vol. 164:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
PROLINE
BIOCHEMICAL REACTION KINETICS
TRITIUM COMPOUNDS
ISOTOPE APPLICATIONS
TYROSINE
AUTORADIOGRAPHY
BIOSYNTHESIS
DENTIN
PRECURSOR
TEETH
AMINES
AMINO ACIDS
AZOLES
CARBOXYLIC ACIDS
DIGESTIVE SYSTEM
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROXY ACIDS
KINETICS
LABELLED COMPOUNDS
ORAL CAVITY
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PYRROLES
PYRROLIDINES
REACTION KINETICS
SYNTHESIS
550601* - Medicine- Unsealed Radionuclides in Diagnostics
550201 - Biochemistry- Tracer Techniques