Loss of response to thyroid hormone in developing nervous tissue correlates with enhanced synthesis of a 25-kilodalton stress protein.
Directly following transfer to in vitro conditions, lumbar dorsal root ganglia (DRG) from triiodothyronine (T3)-treated premetamorphic tadpoles showed an approximately three fold increase in incorporation of bath-applied radiolabeled amino acid relative to DRG from vehicle-treated tadpoles. By contrast, at 1 h after transfer, no increased incorporation was detected. At this time, examination of in-vitro-synthesized [35S]proteins by two-dimensional gel electrophoresis revealed a selective enhancement of a slightly acidic 25-kilodalton (kD) polypeptide. Addition of 1 M glycerol to the incubation medium prevented the enhanced synthesis of the low-molecular-weight polypeptide and preserved the T3 response. When DRG were exposed in situ, the T3 response - monitored following intraganglionic injection of [35S]methionine-was detected after 2 h, but not after 4 h. Four hours were also the earliest time at which an elevated level of the 25-kD polypeptide was observed. The correlation between loss of hormonal responsiveness and appearance of a putative stress protein is of general importance as a cautionary note for in vitro studies of endocrine effects on developing tissues.
Hammerschlag
R
R
Division of Neurosciences, Beckman Research Institute of the City of Hope, Duarte, Calif.
Ando
M
M
Maines
S
S
D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D005727:Ganglia, Spinal / Q000187:drug effects / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000096:biosynthesis*; D007267:Injections; D008715:Methionine / Q000378:metabolism; D009417:Nerve Tissue / Q000378:metabolism*; D011892:Rana catesbeiana; D013963:Thyroid Hormones / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism / Q000494:pharmacology
D006360:Heat-Shock Proteins; D013963:Thyroid Hormones; D014284:Triiodothyronine; D008715:Methionine