[Study of age-specific changes in labeled citrate metabolism in health and disease].

A new coefficient - mineralized tissues/biological fluids (MT/BF) - is suggested for evaluating the distribution of compounds adsorbed by MT and dissolved in BF. The relative radioactivity (RRA) was estimated for the periods of 10 min to 96 h after intraperitoneal injection of [3-(14)C]citrate to rats aged 1 and 3 months and over 1 year by dividing the percent of incorporation in MT by the percent of incorporation in BF. Changes in RRA for molar root/blood serum (R/BS) and RRA for dentin/blood serum (D/BS) are similar: low values at the beginning of experiment, an increase 1 h postinjection, a decrease 2-3 h postinjection, and another increase (65-80 times) by 96 h postinjection. A biphasic reaction with a rapid elevation and decrease after 1-2 h and a second elevation before the end of the experiment due to citrate adsorption on hydroxyapatite and influence of D and R proteins on stable hemosorption of citrate by MT was observed. The time course of RRA enamel/oral fluid was different: a decrease 1 h postinjection and an increase 2-3 h postinjection. Two weeks after crossing the inferior alveolar nerve, the R/BS RRA decreased to a lesser degree in 1-month-old rats in comparison with 3-month-old animals, which can be explained by higher efficiency of the adaptive-compensatory mechanisms in growing rats.