Effect of epinephrine and 5-hydroxytryptamine on in vitro thyroid iodine organification

MASINI-REPISO ANA M, COLEONI ALDO H

ACTA ENDOCRINOLOGICA

Bogtrykkeriet Forum Copenhagen

Lugar: Copenhagen, Denmark; Año: 1981 vol. 97 p. 207 - 207

0001-5598

dir> The effect of epinephrine (E) and 5-hydroxytryptamine (5-HT) on some elements involved in thyroid iodine organification was studied using a bovine thyroid subcellular fraction sedimented at 30 000 g. 131I-incorporation into particulate proteins and into tyrosine was increased by 10(-3) M and 10(-5) M E and 5-HT. This effect was inhibited by 6-n-propyl-2-thiouracil and by catalase. In the presence of these amines the activity of NADPH-cytochrome c reductase was not modified. Both E and 5-HT were able to generate H2O2 when added to the particulate fraction as measured by the oxidation of o-dianisidine. H2O2 generation and [131I]iodotyrosine formation were inhibited by pargyline, a monoamine oxidase (MAO) inhibitor. Tyramine, a specific substrate for thyroid MAO, produced H2O2 and increased [131]iodotyrosine formation. This effect was higher when compared to the effect elicited by E or 5-HT. The stimulatory effects of tyramine were blocke