Vol. 281, Issue 5, E1073-E1081, November 2001
Different role of insulin in GLUT-1 and -4 regulation in heart and skeletal muscle during perinatal
hypothyroidism
S.
Ramos,
L.
Goya,
C.
Alvarez,
M. A.
Martín,
M.
Agote,
F.
Escrivá, and
A. M.
Pascual-Leone
Instituto de Bioquímica (Centro Mixto Consejo Superior
Investigaciones Científicas-Universidad Complutense de
Madrid), Facultad de Farmacia, Ciudad Universitaria, 28040 Madrid, Spain
Two groups of
hypothyroid rats were used; one group was given
2-mercapto-1-methylimidazole (MMI) treatment in the drinking water of
the mothers and was killed at 2 and 4 days of life, and the other group
was given similar MMI treatment and then was thyroidectomized at 5 days
of life and killed at 8 or 20 days. Serum insulin, growth hormone (GH),
and insulin-like growth factor I (IGF-I) were decreased in MMI-treated
rats but increased in MMI-treated plus thyroidectomized rats. No
significant reduction of thyroid hormones was observed in 2-day-old MMI
rats. Protein and mRNA expression of GLUT-1 increased, and those of
GLUT-4 decreased, in the heart in all populations independent of
changes in insulin, GH, and IGF-I levels. However, GLUT-4 protein and
mRNA expression in quadriceps and gastrocnemius skeletal muscles
decreased at 4 days and increased at 8 and 20 days of life in parallel
with insulin, GH, and IGF-I levels. GLUT-1 in the skeletal muscles
seemed regulated posttranscriptionally and presented a decrease of mRNA
expression in all stages studied. A differential sensitivity to insulin
regulation of GLUT-1 and GLUT-4 glucose transporters seems to be one of
the causes for the tissue-specific regulation of these glucose
transporters in heart and skeletal muscles during the perinatal period.
perinatal period; thyroid hormones; GLUT-1 and GLUT-4 regulation; insulin
