TY - JOUR
TI - Long-term thyroxine administration increases heat stress protein-70 mRNA
expression and attenuates p38 MAP kinase activity in response to
ischaemia
AU - Pantos, CI
AU - Malliopoulou, VA
AU - Mourouzis, IS
AU - Karamanoli, EP and
AU - Tzeis, SM
AU - Carageorgiou, HC
AU - Varonos, DD
AU - Cokkinos, DV
JO - HORMONES-INTERNATIONAL JOURNAL OF ENDOCRINOLOGY AND METABOLISM
PY - 2001
VL - 170
TODO - 1
SP - 207-215
PB - SOC ENDOCRINOLOGY
SN - null
TODO - 10.1677/joe.0.1700207
TODO - null
TODO - The present study was undertaken to investigate heat stress protein
(HSP)-70 mRNA induction and p38 MAP kinase (MAPK) activity in response
to ischaemic stress in the hyperthyroid rat heart.
L-Thyroxine (T-4) (25 mug/100g body weight) was administered to Wistar
rats for 2 days (THYRacute) or 14 days (THYR), while animals treated
similarly with normal saline served as controls (NORMacute and NORM). In
addition, abdominal aortic banding was performed in another group of
rats to produce constriction-induced hypertrophy (HYP), while
sham-operated (SOP) animals served as controls. Isolated rat hearts were
perfused in a Langendorff mode. Hearts from NORMacute (n = 6), THYRacute
animals (n = 8), NORM (n = 6), THYR (n = 6), SOP (n = 5) and HYP (n = 7)
animals were subjected to 20 min of zero-flow global ischaemia followed
by 45 min of reperfusion. HSP70 mRNA expression and phosphorylated p38
MAPK protein expression were detected in response to ischaemia and
protein kinase C-epsilon (PKC epsilon) protein expression was detected
at baseline. Thyroid hormones were measured in plasma.
Long-term T-4 administration and aortic constriction resulted in the
development of cardiac hypertrophy. Thyroid hormones were increased in
both THYR and THYRacute as compared with normal groups (P < 005). HSP70
mRNA induction was increased 2.3-fold in THYR as compared with NORM
hearts (P < 0.05), whereas there was not any difference between
THYRacute and NORMacute hearts (P > 0.05). Phosphorylated p38 MAPK
protein expression was 22-fold more in NORM than in THYR hearts (P <
0.05), but it was not different between NORMacute and THYRacute hearts
(P > 0.05). HSP70 mRNA induction was 1.8-fold greater in HYP than in SOP
hearts (P < 0.05), whereas phosphorylated p38 MAPK protein expression
was similar between the two groups (P > 0.05). PKC epsilon protein
expression at baseline was 1.7-fold more in NORM than in THYR hearts (P
< 0.05), and not different between NORMacute and THYRacute hearts (P >
0.05) as well as HYP and SOP hearts (P > 0.05).
This study shows that HSP70 mRNA expression is increased, whereas p38
MAPK activation is attenuated in response to ischaemia in long-term
T-4-treated rat hearts as compared with normal and acute hyperthyroid
hearts.
ER -