Reverse triiodothyronine in the chicken

Bn, Premachandra; Lang, Stanley; Andrada, J.A.; Kite, Jr Jh

doi:10.1016/0024-3205(77)90303-4

Cited by 15 publications

(1 citation statement)

References 22 publications

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“…The observed increase in rT, during the 2nd week of life would be asso ciated with the maturation of the enzyme sys tem or with its increasing activity. It is of interest to note that an increase in rT, pro duction with age has been found also in chickens [Premachandra et al, 1970] which, from the point of view of the mediating role of hormones in postnatal thermogenesis, dis play some common features with piglets in that they have no brown adipose tissue and do not react with O, consumption to NA injection [Freeman, 1966[Freeman, , 1970. On com parison the pig and the chicken represent the 'thyroxine-type' in contrast to the 'noradren aline-type' of newborns [Slebodzinski, 1975b],…”

Section: Discussionmentioning

confidence: 99%

Sequential Observation of Changes in Thyroxine, Triiodothyronine and Reverse Triiodothyronine during the Postnatal Adaptation of the Pig

1981

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Principal serum iodothyronines, T₄, T₃ and rT₃, have been simultaneously measured by a specific radioimmunoassay in piglets kept for sequential observation with the mother from 1 to 21 days of age. During several hours postnatally, a high concentration of the hormone was noted as a result of an enhanced secretory activity of the thyroid gland. Later, a progressive decrease with a nadir at about day 3 was observed, followed by a second rise in the hormone level. Changes in T₃ and rT₃ levels from birth to the end of the 1st week, paralleled those for T₄. The T₃:rT₃ ratio of about 2 during the 1st week fell to about 1.5 during the 3rd week as a result of the progressive increase in rT₃ and decrease in T₃ concentrations. The T₄:rT₃ ratio fell with the progressing age to the level observed in post-weaned pigs. At birth, the newborn pig seems to possess a low capability of 5-deiodinase enzyme system thus the converting enzymes first work towards T₄–T₃ conversion while T₄–rT₃-converting ability progressively increases with age. The role of this variability for the neonatal thermogenic stability is discussed.