Thyroid Hormones affect the Level and Activity of Nitric Oxide Synthase in Rat Cerebral Cortex during Postnatal Development
The effects of thyroid hormones (TH) on the enzyme level and activity of neuronal nitric oxide synthase (nNOS) were studied in the rat cerebral cortex during postnatal life. As revealed by arginine/citrulline conversion assay and Western blot analysis of the homogenate of the parietal cortex T4 significantly increased nNOS activity and nNOS protein level to 153 ± 25% and to 178 ± 20%, respectively. In contrast, 6-n-propyl-2-thyouracil (PTU) decreased nNOS activity and nNOS level to 45 ± 10% and to 19 ± 4%, respectively. The number of nNOS-immunoreactive neurons did not change after either T4 or PTU treatment, however, following T4 administration the percentage of intensively immunoreactive neurons increased to 85 ± 3% compared to control (65 ± 6%), whereas it decreased to 49 ± 2% after PTU treatment. Our findings indicate that abnormal TH levels differentially regulate the activity and the level of nNOS and suggest a cross-talk between the TH and NO signaling pathway in the developing cerebral cortex of rats.
KeywordsCerebral cortex Development Nitric oxide synthase Thyroid hormone
The substantial contribution of Dr Ágota Lenkey (Institute of Clinical Biochemistry and Molecular Pathology, Medical and Health Science Center, University of Debrecen, Hungary) in the measurement of serum fT4 and TSH level, and Dr Mária Földvári (Veszprém Central Laboratory, Prodia Diagnostic Rt, Veszprém, Hungary) in the determination of total T4 and T3 concentration in the cortical samples is greatly appreciated. This work was supported by the Universitas Foundation 2000 from the University of Debrecen to Z.S., the Mecenatura 5/99 grant from the Medical and Health Science Center at the University of Debrecen to K.P., the Hungarian Scientific Research Fund T49090 to K.E., and ETT 244/2006 grant from the Ministry of Health to F.E.
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