Iodothyronine 5'-deiodinating activity in the pineal gland

Juan M. Guerrero, Russel J. Reiter

Research output: Contribution to journalShort surveypeer-review

22 Scopus citations

Abstract

1. 1. The presence of an iodothyronine 5'-deiodinating activity has been described in the pineal gland of various rodents, and it has been identified as a type II 5'-deiodinase isoenzyme since it is relatively insensitive to inhibition by propylthiouracil and its activity increases during hypothyroidism. 2. 2. 5'-Deiodinase activity in the rat pineal gland follows a nyctohemeral profile, exhibiting basal values during the day and maximal values at night. The nocturnal increase is dependent on the noradrenergic input from the superior cervical ganglia, and both in vivo and in vitro studies show that β-adrenergic receptors are primarily involved in the activation of the enzyme. 3. 3. Day-night differences in rat pineal 5'-deiodinase activity are found beginning at 2 weeks of age, with rhythms increasing in amplitude until maximal differences are reached in adult animals. During the maturation of the rhythm, changes in regulation of enzyme activation are observed. Thus, during the first 2-3 weeks of age, α-adrenergic receptors appear to be as important as β-adrenergic receptors in regulating the deiodinating activity of the pineal. However, in adults, no role of α-adrenergic receptors has been described. 4. 4. Although regulation of 5'-deiodinase activity in the pineal gland is well established, few data are available concerning the physiological significance of the enzyme in the gland. Of the studies that have been performed, those attempting to demonstrate a relationship between pineal 5'-deiodinase activity and other pineal rhythms e.g. those of melatonin production and N-acetyltransferase activity, indicates that the latter rhythms do not rely on the cyclic production of T3. The alternate possibility that the 5'D rhythm depends on the cyclic production of melatonin remains to be examined.

Original languageEnglish (US)
Pages (from-to)1513-1523
Number of pages11
JournalInternational Journal of Biochemistry
Volume24
Issue number10
DOIs
StatePublished - Oct 1992

ASJC Scopus subject areas

  • Biochemistry

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