Uptake of triiodothyroacetic acid and its effect on thyrotropin secretion in cultured anterior pituitary cells.

We reported evidence for carrier-mediated uptake of T3 and Tq in cultured anterior pituitary cells of euthyroid rats

M E Everts; T J Visser; E P Moerings; R Docter; H van Toor; A M Tempelaars; M de Jong; E P Krenning; G Hennemann

2014

Under pathological conditions, as, for example, fasting, triiodothyroacetic acid production is substantially increased. These researchers suggested that Triac might be of importance for the suppressionof TSH secretion in fasting, which occursdespite low plasmaTJ and T4 levels
To determine whether TX, Tq, or Triac affected basal TSH release from cultured anterior pituitary cells, these three hormones were added at a concentration of 10 nM to cells cultured in medium supplemented with absorbed fetal calf serum
The stimulating effect of TRH on TSH release was almost completely blocked by preincubation and incubation with 10 nM or 1 PM T3 or Triac
We tested within one experiment the effects of Triac, T3, and T4 on TRH-induced TSH release at lower concentrations than those of the previous series.The results shown in Table 3 demonstrate that at concentrations of 1, 2.5, and 10 nM, T3 and Triac were potent in suppression of the TRH-induced TSH release.Tl, had no significant inhibitory effect at a concentration of 2.5 nM
The presence of 10 nM Triac resulted in significantly lower uptake of Triac, whereas 10 PM Triac produced a maximal inhibitory effect of 56%
The results of the present study demonstrate that Triac is rapidly taken up by the pituitary
The 15-n-tintriiodothyroacetic acid uptake was reduced by simultaneous incubation with unlabeled Triac at concentrations as low as 10 nM, suggesting the existence of a carrier in the pituitary cell membrane

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