AJP - Endocrinology and Metabolism, Vol 264, Issue 5 E804-E809, Copyright © 1993 by American Physiological Society
Triiodothyronine receptor complex in developing rat brain and pituitary
M. Rodriguez and T. Jolin
Instituto de Investigaciones Biomedicas, Madrid, Spain.
In vitro saturation analysis combined with nuclear 3,5,3'-triiodothyronine
(T3) quantification was used to examine the changes in T3 binding
parameters in rat pituitary and cerebrocortical nuclei from fetal day 14 to
postnatal day 20. T3 receptors were first detectable in neuronal, glial,
and pituitary nuclei on fetal days 14, 17, and 18, respectively. Thereafter
T3 receptor concentrations in neuronal, glial, and pituitary nuclei
increased throughout the developmental period studied, reaching maximal
levels during neonatal life (1,129, 1,025, and 635 fmol/mg DNA,
respectively). T3 levels in pituitary, neuronal, and glial nuclei also
increased during development there being a 35-, 34-, and 120-fold rise
between fetal days 16-18 and the 20th postnatal day. Endogenous T3 receptor
occupancy throughout the experimental period increased six- to ninefold in
the three types of nuclei. The presence of T3 receptor complex in the
pituitary and cerebrocortical nuclei during perinatal development lends
further support to the hypothesis that T3 may be an important factor in
determining the differentiation and development of these cells.
