Thiamine content and turnover rates of some rat nervous regions, using labeled thiamine as a tracer

Abstract

The content of total thiamine radioactivity in some nervous structures and liver of the rat was determined in a steady state condition, using [thiazole-2-14C]thiamine as a tracer. The contents were analyzed by a mamillary type compartmental model which enabled us to calculate the influx and efflux fractional rate constants, turnover times, turnover rates and relative accuracy. Total thiamine turnover rates of the central nervous system regions were found to be ordered in the following sequence: cerebellum (0.55 μg/g·h) > medulla and pons > spinal cord and hypothalamus > midbrain (plus thalamic area) and corpus striatum > cerebral cortex (0.16 μg/g·h). Sciatic nerve turnover rate was 0.58 μg/g·h. The turnover times were mainly between 5 and 10 h (range 2.4–16.4 h). The influx rate constants could be ordered as follows: cerebellum > hypothalamus, pons and medulla > corpus striatum, spinal cord, midbrain (plus thalamic area) and sciatic nerve > cerebral cortex. The results show in general a good agreement between turnover rate values and brain regional sensitivity to thiamine deficiency, the most vulnerable areas to thiamine depletion being those with the highest turnover rates.