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Nuclear and Cytoplasmic Triiodothyronine‐Binding Sites in Primary Sensory Neurons and Schwann Cells: Radioautographic Study During Development
Author(s) -
Walter I. Barakat,
Droz B.
Publication year - 1995
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1995.tb00675.x
Subject(s) - receptor , dorsal root ganglion , biology , medicine , endocrinology , sciatic nerve , microbiology and biotechnology , sensory system , neuroscience , anatomy
The effects of the thyroid hormones on target cells are mediated through nuclear T 3 receptors. In the peripheral nervous system, nuclear T 3 receptors were previously detected with the monoclonal antibody 283 rnAb in all the primary sensory neurons throughout neuronal life and in peripheral glia at the perinatal period only (Eur. J. Neurosci. 5, 379, 7993). To determine whether these nuclear T 3 receptors correspond to functional ones able to bind T 3 , cryostat sections and in vitro cell cultures of dorsal root ganglion (DRG) or sciatic nerve were incubated with 0.1 nM [1251]‐labeled T 3 , either alone to visualize the total T 3 ‐binding sites or added with a lo3 fold excess of unlabeled T 3 to estimate the part due to the non‐specific T 3 ‐binding. After glutaraldehyde fixation, radioautography showed that the specific T 3 ‐binding sites were largely prevalent. The T 3 ‐binding capacity of peripheral glia in DRG and sciatic nerve was restricted to the perinatal period in vivo and to Schwann cells cultured in vitro. In all the primary sensory neurons, specific T 3 ‐binding sites were disclosed in foetal as well as adult rats. The detection of the T 3 ‐binding sites in the nucleus indicated that the nuclear T 3 receptors are functional. Moreover the concomitant presence of both T 3 ‐binding sites and T 3 receptors CI isoforms in the perikaryon of DRG neurons infers that: 1) [1251]‐labeied T 3 can be retained on the T 3 ‐binding ‘E’ domain of nascent CI, isoform molecules newly‐synthesized on the perikaryal ribosomes; 2) the CI isoforms translocated to the nucleus are modified by posttranslational changes and finally recognized by 2B3 rnAb as nuclear T 3 receptor. In conclusion, the radioautographic visualization of the T 3 ‐binding sites in peripheral neurons and glia confirms that the nuclear T 3 receptors are functional and contributes to clarify t h e discordant intracellular localization provided by the immunocytochemical detection of nuclear T 3 receptors and T 3 receptor CI isoforms.