Endocrinology, Vol 124, 1026-1032, Copyright © 1989 by Endocrine Society
3,5,3'-Triiodothyronine determines the viability of GC cells after heat shock
LE Shapiro, SH Wasserman, CP Katz and MI Surks
Department of Medicine, Montefiore Medical Center, Bronx, New York 10467.
The heat shock (HS) response is a characteristic disruption of protein
synthesis which occurs in cells exposed to a variety of noxious stimuli.
The effects of HS on thyroid hormone-responsive GC cells were studied in an
attempt to devise an in vitro model for the adaptive changes in thyroid
hormone action caused by nonthyroidal disease. HS enhanced GC cell
synthesis of 70 K and 90 K proteins in a manner previously described as
characteristic of the HS response in many tissues. A step-wise decrease in
GC cell viability occurred when cells were exposed to 45 C for 10 to 35
min. HS (45 C, 20 min) resulted in a rapid decrease in binding of T3 to
nuclear receptors. Two hours after HS, analysis of T3 binding to isolated
nuclei showed a 50% fall in binding capacity (240 fmol/100 micrograms DNA)
compared to non-HS control cells (540 fmol/100 micrograms DNA); no
difference in dissociation constant (Kd) was observed. The effect of
thyroid hormone on cell viability after HS was then determined. Thyroid
hormone depletion (less than or equal to 0.02 nM T3) resulted in
significantly (P less than 0.05) enhanced cell viability compared to cells
cultured with physiological T3 (0.2 nM) after incubation at 45 C for
intervals of 10-35 min. This inverse relationship between medium T3 content
and cell tolerance of HS occurred over a wide range of T3 concentrations.
Mean cell viability after exposure to 45 C for 20 min was 44 +/- 3% in
T3-depleted cultures (less than or equal to 0.02 nM), 27 +/- 1% to 32 +/-
5% in cultures containing 0.07-0.5 nM T3, and 13 +/- 3% in cultures
containing 5 nM T3. Our results thus characterize the response to HS in GC
cells and the relationship of this response to medium T3. Similar to the
effect of various nonthyroidal diseases on rat hepatocytes in vivo, HS
resulted in a decrease in T3 nuclear receptors. Similar to the adverse
effect of thyroid hormone on morbidity in animals with experimental
diseases or injury, GC cell viability after HS was inversely related to
medium T3 content. Thus the HS response in GC cells may be a valuable in
vitro model relevant to the effect on thyroid hormone action caused by
nonthyroidal disease.