Monoamine oxidase activity and triiodothyronine biosynthesis in human cultured thyroid cells

Kraiem, Zaki; Sadeh, O.; Youdim, Moussa B. H.

doi:10.1111/j.1476-5381.1989.tb11839.x

Cited by 6 publications

(6 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The pat¬ tern of MAO in the adult and the last fetal stages is dif¬ ferent from that exhibited by TPO and iodide organifica¬ tion, a finding that reinforces previous evidence indicating no direct relation between MAO activity and thyroid hor¬ mone biosynthesis (8,10,11). It is unknown whether dif¬ ferences in structure or localization between fetal and adult thyroid MAO might account for the failure to detect it cy¬ tochemically at late gestation where the level of the enzyme was similar to that in the adult.…”

Section: Fig 5 (Continued)supporting

confidence: 68%

“…However, evidence against a TSH regulation for the latter enzyme has been reported recently (9). Prev.ous reports suggested a role of MAO and NADPH-cy-MATERIALS AND METHODS tochrome c reductase in H2O2 generation (1), although this hypothesis was not further supported (8)(9)(10)(11). T-The ontogenesis of thyroid function has been studied in several species, and sequential developmental steps in the Fetal and adult bovine thyroid glands were obtained at biochemical maturation have been described (12)(13)(14)(15)(16).…”

mentioning

confidence: 98%

See 1 more Smart Citation

Biochemical and Functional Changes During the Bovine Fetal Thyroid Development

Masini-Repiso

Orgnero-Gaisán²,

Bonaterra³

et al. 1998

Thyroid

View full text Add to dashboard Cite

To establish biochemical and functional relations during thyroid development, the activity of thyroid peroxidase (TPO), nicotinamide adenine dinucleotide phosphate (NADPH)-cytochrome c reductase and monoamine oxidase (MAO) in a particulate fraction and the iodide transport and organification in slices of bovine fetal thyroid were examined throughout gestation. The cytochemical localization of TPO, H2O2 generating sites and MAO was also studied. Fetal glands were grouped in stages I to V according to increasing developmental features; adult tissues were also analyzed. TPO activity in each of the fetal stages was higher than in the adult; a marked increase was observed in stages IV and V. Iodide transport (T/M) was similar in stages I to V and the adult. Iodide organification in fetal thyroids showed a similar pattern to that of TPO activity. When compared with the adult, at midgestation (stages II to III), a lower iodination coexisted with a higher TPO activity. The activity of NADPH-cytochrome c reductase and MAO, two enzymes previously proposed to participate in thyroid H2O2 generation, did not parallel the level of iodide organification. Cells from stages II to V exhibited a positive cytochemical reaction for TPO in the rough endoplasmic reticulum (RER) and the perinuclear cisternae (PC). In stages IV, V, and adult, TPO was occasionally found in apical vesicles and microvilli, whereas H2O2 was detected within the RER and the PC. MAO reaction was positive in adult, but not in fetal thyroid. These results indicate that a high TPO activity accompanied the onset of the organification process during fetal thyroid development. The level of iodination was associated with the presence of TPO at a proper site rather than to the level of TPO activity. Evidence against a role of NADPH-cytochrome c reductase and MAO in the iodide organification was obtained.

show abstract

Section: Fig 5 (Continued)supporting

confidence: 68%

mentioning

confidence: 98%

Biochemical and Functional Changes During the Bovine Fetal Thyroid Development

Masini-Repiso

Orgnero-Gaisán²,

Bonaterra³

et al. 1998

Thyroid

View full text Add to dashboard Cite

show abstract

“…A predominance of type-MAO in the rat thyroid had been suggested by Knopp & Torda (1983). A recent report indicates the presence of MAO-and -B in human cultured thy¬ roid cells, although the relative proportion of each form was not established (Kraiem et al 1989). …”

Section: Iodide Organification In Vivomentioning

confidence: 93%

“…However, no further evi¬ dence for the participation of MAO in H20, production has been given. Moreover, a recent report indicates that MAO inhibitors failed to inhibit 3,5,3'-tri-iodo-L-thyronine (T3) secretion in human cultured thyroid cells (Kraiem, Sadeh & Youdim, 1989), giving rise to doubts about the role of MAO in thyroid hormone biosynthesis. Two types of MAO activities (A and B) have been identified in different tissues (Fowler & Ross, 1984) on the basis of their substrate specificity and inhibitor sensitivity which, in turn, allows for estimation of the relative proportions of both forms of the enzyme.…”

Section: Introductionmentioning

confidence: 99%

Rat thyroid monoamine oxidase (MAO) is regulated by thyrotrophin: evidence that the main form of the enzyme (MAO-A) is not directly involved in iodide organification

Cabanillas

Masini-Repiso²,

Coleoni³

1991

Journal of Endocrinology

View full text Add to dashboard Cite

The characteristics and regulation of monoamine oxidase (MAO) were studied in rat thyroid tissue. A measured Michaelis constant (Km) value of 102 mumol/l was similar to the Km values found in other tissues. Maximal velocity (Vmax) was 1.028 nmol/mg protein per min. It is known that MAO is present as two isoenzymes, A and B, which are sensitive to clorgyline and deprenyl respectively. The in-vitro effect of graded concentrations of these selective MAO inhibitors was used to estimate the relative proportion of A and B isoenzymes. Clorgyline strongly decreased thyroid MAO activity at concentrations as low as 1 pmol/l while the effect of deprenyl was observed only at concentrations higher than 10 mumol/l. These results indicated that MAO-A is the main form of the enzyme in the rat thyroid. In-vivo administration of L-thyroxine (5.6-224 nmol/kg) significantly reduced thyroid MAO activity at doses equal to or greater than those which have been reported to inhibit iodine output from the thyroid. Increased TSH levels, induced either by exogenous TSH or methimazole administration, resulted in a significant increase in thyroid MAO activity. Theophylline, a phosphodiesterase inhibitor and dibutyryl cyclic AMP were also able to stimulate MAO activity when administered in vivo. Iodide organification (protein-bound 131I) in vivo as well as the relative proportion of the different thyroid iodo-compounds were not affected in animals with reduced or increased thyroid MAO activity induced by clorgyline or theophylline respectively. It was concluded that rat thyroid MAO activity is under the influence of TSH.(ABSTRACT TRUNCATED AT 250 WORDS)

show abstract

“…Besides 3-T 1 AM, another interesting candidate - also known as an activating Taar1 ligand - is tyramine [51], which was previously proposed to be involved in the generation of H 2 O 2 at the apical pole of thyrocytes [52,53]. However, an answer to the open question as to which of the biogenic amines that are known to trigger Taar1 in vitro may be important in situ for thyroid regulation depends on the availability of methods to qualitatively and quantitatively determine the amounts of intrathyroidal biogenic amines.…”

Section: Discussionmentioning

confidence: 99%

Trace Amine-Associated Receptor 1 Localization at the Apical Plasma Membrane Domain of Fisher Rat Thyroid Epithelial Cells Is Confined to Cilia

Szumska¹,

Qatato²,

Rehders³

et al. 2015

Eur Thyroid J

View full text Add to dashboard Cite

Background: The trace amine-associated receptor 1 (Taar1) is one member of the Taar family of G-protein-coupled receptors (GPCR) accepting various biogenic amines as ligands. It has been proposed that Taar1 mediates rapid, membrane-initiated effects of thyronamines, the endogenous decarboxylated and deiodinated relatives of the classical thyroid hormones T₄ and T₃. Objectives: Although the physiological actions of thyronamines in general and 3-iodothyronamine (T₁AM) in particular are incompletely understood, studies published to date suggest that synthetic T₁AM-activated Taar1 signaling antagonizes thyromimetic effects exerted by T₃. However, the location of Taar1 is currently unknown. Methods: To fill this gap in our knowledge we employed immunofluorescence microscopy and a polyclonal antibody to detect Taar1 protein expression in thyroid tissue from Fisher rats, wild-type and taar1-deficient mice, and in the polarized FRT cells. Results: With this approach we found that Taar1 is expressed in the membranes of subcellular compartments of the secretory pathway and on the apical plasma membrane of FRT cells. Three-dimensional analyses further revealed Taar1 immunoreactivity in cilial extensions of postconfluent FRT cell cultures that had formed follicle-like structures. Conclusions: The results suggest Taar1 transport along the secretory pathway and its accumulation in the primary cilium of thyrocytes. These findings are of significance considering the increasing interest in the role of cilia in harboring functional GPCR. We hypothesize that thyronamines can reach and activate Taar1 in thyroid follicular epithelia by acting from within the thyroid follicle lumen, their potential site of synthesis, as part of a nonclassical mechanism of thyroid autoregulation.

show abstract

Monoamine oxidase activity and triiodothyronine biosynthesis in human cultured thyroid cells

Cited by 6 publications

References 20 publications

Biochemical and Functional Changes During the Bovine Fetal Thyroid Development

Biochemical and Functional Changes During the Bovine Fetal Thyroid Development

Rat thyroid monoamine oxidase (MAO) is regulated by thyrotrophin: evidence that the main form of the enzyme (MAO-A) is not directly involved in iodide organification

Trace Amine-Associated Receptor 1 Localization at the Apical Plasma Membrane Domain of Fisher Rat Thyroid Epithelial Cells Is Confined to Cilia

Contact Info

Product

Resources

About