Kinetics of the iodide trapping mechanism in normal and pathological human thyroid slices

Abstract

Kinetics of the iodide trapping mechanism in thyroid slices was studied in human and animal tissues. Slices were incubated with several medium iodide concentrations, ranging from 5 \m=x\10\m=-\6 m to 2 \m=x\10\m=-\4 m, in order to calculate in the steady state the following kinetic parameters of the iodide transport: Km, maximal capacity (C) and diffusion factor (D).Results indicated that the Km was similar in magnitude (10\m=-\5 m) in all cases where trapping activity was present, while maximal capacity (C) values showed significant differences between those pathologies in which trapping activity was hyperstimulated (dishormonogenetic goitre, Graves' disease, toxic adenoma) and those where thyroid tissues presented focal or total alterations on its structure (non-toxic nodular goitre, Hashimoto's thyroiditis, thyroid cancer) or where thyroid tissues were not sufficiently stimulated by TSH (extranodular tissue of toxic adenoma). 'Warm' nodules were not significantly different from normal human thyroid. These results suggest that the scattered trapping values observed in the different thyroid pathologies correspond to quantitative differences between them rather than to qualitative alterations in the thyroid iodide pump.

Rescue, propagation, and partial purification of a helper virus-dependent adenovirus vector.

“…Third, hybrid viruses between simian virus 40 (SV40) and AdS have also been reported. One of the viruses comprised only 3.5 kb of DNA from the left end of AdS and 5.5 copies of SV40 DNA with a total size of 35 kb (21). In addition, the smallest genome size among different types of AdS/SV40 chimeric viruses was -25 kb (22).…”

Competitive Inhibition of Thyroidal Uptake of Dietary Iodide by Perchlorate Does Not Describe Perturbations in Rat Serum Total T 4 and TSH

“…We previously simultaneously optimized V max T i (nanomoles per hour) and K NIS TSH (nanomoles per liter) (McLanahan et al 2008) to euthyroid, dietary-iodine–sufficient (~ 20 μg/day) rat data for serum and thyroid iodide reported by Eng et al (1999) and McLanahan et al (2007), respectively. The other parameter, NIS affinity constant for iodide ( K m i , nanomoles per liter) in Equation 1 was obtained from Gluzman and Niepomniszcze (1983) as reported by McLanahan et al (2008).…”

Influence of thyroid hormones on nervous system development – brief review

“…First, iodine is absorbed on diet by digestory tract e transported by proteins of basal membrane from follicular cells into the cytoplasm keeping the intracellular iodine concentration always higher than in the extracellular fluid [6]. Once iodine uptake ion occurs, the I -captured by the follicular cell migrates to the apical surface, where it is oxidized and converted to its active form (I + ) by the enzyme thyroid peroxidase [7,8].…”

“…The thyroid peroxidase enzyme is responsible for catalyzing the incorporation of I + to tyrosine residues and the binding of iodotyrosine molecules (already incorporated) in thyroglobulin (phenomenon known as organification) [9]. The now iodinated tyrosine molecules are grouped forming the molecules of thyroid hormones [5,6] One diiodotyrosine added to one monoiodotyrosine results in 3,5,3 triiodothyronine (T3); whilst two diiodotyrosine will form thyroxine (T4) [9]. The hormone triiodothyronine (T3) is less abundant, but it has a much higher biological activity than thyroxine (T4) [10], [11].…”