Serum thyroid hormones and tissue 5'-monodeiodinase activity in acutely thyroidectomized newborn lambs
After either total thyroidectomy or sham operation in full-term fetal sheep, fetuses were delivered and serial blood samples were obtained for measurements of thyroxine (T4), triiodothyronine (T3), and catecholamines. Despite comparable serum T4 values, serum T3 values were lower in the thyroidectomized animals. Four hours after birth, the animals were killed with an intravenous overdose of barbiturate. Brain, thyroid, liver, kidney, and brown adipose tissues were dissected and analyzed for thyroxine 5'-monodeiodinase (5'-MDI) activity in vitro. 5'-MDI activity was comparable in all tissues from sham-operated and thyroidectomized lambs. Plasma epinephrine and norepinehprine concentrations, mean arterial pressure, mean pulse, rectal temperature, and arterial blood gas values were similar in the two groups of animals. These data support the hypothesis that the thyroid gland is the major source of T3 for the T3 surge in the immediate newborn period. They also indicate that the neonatal T3 surge has limited immediate metabolic significance in euthyroid newborns.
- Research Organization:
- Harbor-UCLA Medical Center, Torrance, CA
- OSTI ID:
- 6294176
- Journal Information:
- Am. J. Physiol.; (United States), Vol. 251:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ADRENALINE
RADIOENZYMATIC ASSAY
NEONATES
PHYSIOLOGY
NORADRENALINE
THYROXINE
RADIOIMMUNOASSAY
TRIIODOTHYRONINE
ADIPOSE TISSUE
BLOOD PRESSURE
BRAIN
CATECHOLAMINES
ENZYME ACTIVITY
KIDNEYS
LIVER
REPRODUCTION
SHEEP
THYROID
THYROIDECTOMY
ADRENAL HORMONES
AMINES
AMINO ACIDS
ANIMAL TISSUES
ANIMALS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
BODY
CARBOXYLIC ACIDS
CARDIOTONICS
CARDIOVASCULAR AGENTS
CENTRAL NERVOUS SYSTEM
CONNECTIVE TISSUE
DIGESTIVE SYSTEM
DOMESTIC ANIMALS
DRUGS
ENDOCRINE GLANDS
GLANDS
HORMONES
HYDROXY COMPOUNDS
IMMUNOASSAY
IMMUNOLOGY
ISOTOPE APPLICATIONS
MAMMALS
MEDICINE
NERVOUS SYSTEM
NEUROREGULATORS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
ORGANS
PEPTIDE HORMONES
PHENOLS
POLYPHENOLS
RADIOASSAY
RADIOIMMUNOLOGY
RUMINANTS
STEROID HORMONES
SURGERY
SYMPATHOMIMETICS
THYROID HORMONES
TISSUES
TRACER TECHNIQUES
VERTEBRATES
550601* - Medicine- Unsealed Radionuclides in Diagnostics
551001 - Physiological Systems- Tracer Techniques