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As we previously obtained evidence that insulin-like growth factor-I (IGF-I) inhibits T3-induced GH secretion and GH mRNA expression without affecting basal GH secretion in thyroidectomized rat pituitary cells grown in hypothyroid medium, we examined changes in IGF-I receptors in the pituitary gland, as induced by thyroid hormone. Thyroidectomized rats and a quantitative receptor autoradiographic method were used. The density of [125I]IGF-I-binding sites in the anterior pituitary gland decreased 4 weeks after thyroidectomy; that is a significant decrease in the number of the receptors compared to findings in control rats (P less than 0.01). The affinity (Kd) remained unchanged. There were no changes in binding parameters in the ventroposterior thalamic nucleus in the brain, renal cortex, and liver parenchyma. The ip administration of T4 once a day (48 micrograms/kg) for 1-2 weeks compensated for the decrease in the binding capacity of [125I]IGF-I-binding sites to that of the control values (P less than 0.01). We propose that IGF-I receptors in the anterior pituitary gland may be regulated by thyroid hormone.
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S Yamashita, and
M Niwa, and
M Kurihara, and
S Harakawa, and
M Izumi, and
S Nagataki, and
S Melmed
August 1993,
Annals of the New York Academy of Sciences,
K Matsuo, and
S Yamashita, and
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M Kurihara, and
S Harakawa, and
M Izumi, and
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S Melmed
April 2005,
Regulatory peptides,
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June 1989,
Journal of neuroendocrinology,
K Matsuo, and
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M Izumi, and
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S Melmed
November 1990,
The Journal of clinical endocrinology and metabolism,
K Matsuo, and
S Yamashita, and
M Niwa, and
M Kurihara, and
S Harakawa, and
M Izumi, and
S Nagataki, and
S Melmed
June 1991,
The American journal of physiology,
K Matsuo, and
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July 1991,
Molecular endocrinology (Baltimore, Md.),
K Matsuo, and
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M Niwa, and
M Kurihara, and
S Harakawa, and
M Izumi, and
S Nagataki, and
S Melmed
January 1989,
The Journal of endocrinology,
K Matsuo, and
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M Niwa, and
M Kurihara, and
S Harakawa, and
M Izumi, and
S Nagataki, and
S Melmed
August 1986,
The Journal of biological chemistry,
K Matsuo, and
S Yamashita, and
M Niwa, and
M Kurihara, and
S Harakawa, and
M Izumi, and
S Nagataki, and
S Melmed
October 2001,
Journal of dental research,
K Matsuo, and
S Yamashita, and
M Niwa, and
M Kurihara, and
S Harakawa, and
M Izumi, and
S Nagataki, and
S Melmed
December 1991,
The Journal of laboratory and clinical medicine,
