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E Vigouroux

Publications and source records attributed to E Vigouroux.

16 recordsLinked to original sources
PubMed2000

Revised T3 uptake and T4-to-T3 conversion in brain and cerebellum of 10-day-old rats: a compartment analysis.

The peripheral and cerebral metabolism of thyroid hormones in 10-day-old rats was evaluated by measuring the kinetics of thyroxine (T4) and 3,5,3'-triiodothyronine (T3) fluxes. Labeled iodo-compounds were measured in the plasma, cerebellum and brain (without cerebellum) for 24 hours after the intravenous injection of [125I]T4 plus [131I]T3. Data were interpreted by compartment analysis. T4 was produced at 8.93 pmol x h(-1) and T3 at 2.26 pmol x h(-1) for 22.7 g body weight. The T4 and T3 distribution volumes were 4.26 and 22.7 ml, whereas the extra-cellular fluid volume was 9.42 ml. T4 was therefore considered to be mostly extra-cellular and T3 mostly intracellular. This was confirmed in the brain and cerebellum, where the extra-cellular fluid (ECF) fraction was 0.021 ml/g organ and the tissue-to-plasma ratio of labeled and endogenous hormones was 0.54-6.54 ml plasma/g tissue for T3 and 0.048-0.136 ml plasma/g tissue for T4. The T3 in the brain and cerebellum was distributed in several pools. The first, representing 11% of the cerebellum and 8% of the brain (without cerebellum) T3, was quickly exchanged with circulating T3. The second pool, derived from the local T4 5'-deiodination, represented 48% of the cerebellum and 94% of the brain (without cerebellum) hormone; a possible third pool (41% of the hormonal content) in the cerebellum appeared to be unlabeled by radioactive T3, and motionless. The in vivo T4 to T3 conversion, as a function of weight, accounted for 21% of cerebellum needs and 43% of brain needs. The rest was provided by T3 uptake.

Animals↗
PubMed1999

5'-deiodinase activity in cultured glial and fibroblastic cells from the cerebella of newborn rats.

The cerebellum of young rats contains significant 5'-deiodinase (5'-D) activity, but technical difficulties have made it impossible to identify the enzyme in cultured cerebellar astrocytes. We have developed a culture method which allows cerebellar astrocytes from 6-day-old rats to grow and develop 5'-D activity. Astrocytes cultured for 2 weeks in medium containing 3.25 microM reduced glutathione (GSH) and 0.21 microM vitamin E (VitE) as alpha-tocopherol had 5'-D activity which was stimulated by 1 mM dibutyryl cyclic adenosine monophosphate (dBcAMP) given 16 hours before measuring enzyme activity. Cells cultured without GSH and VitE showed little 5'-D activity, which was not stimulated by dBcAMP Primary cultures of cerebellar astrocytes were cultured for four weeks with or without GSH+VitE, and stimulated by dBcAMP had high 5'-D activity, but were also sometimes contaminated with fibroblasts. The effect of such contamination on the astrocyte 5'-D activity was assessed by preparing primary cultures of fibroblasts from the meninges surrounding 6-day-old rat cerebella. They were grown in the same media and under the same conditions as the astrocytes. The cultured fibroblasts had 5'-D activity independent of GSH+VitE or culture time. The 5'-D activity of both cell populations could be type II 5'-deiodinase (5'-DII) because it was not inhibited by 6-n-propylthiouracil (PTU). Thus, cerebellar astrocytes cultured for 2 weeks in medium containing GSH and VitE have 5'-DII activity. Prolonged cultures favor enzyme activity, but also enhance contamination with fibroblasts, which may also show 5'-DII activity.

Animals↗
PubMed1995

[Analysis of iodine compounds in young rat skin in the period of suckling and in the adult. Effect of perchlorate].

In the suckling and adult rats equilibrated or no by 125I, cutaneous iodine analysed by dialysis and chromatography techniques (Dowex and Sephadex) was the purpose of this study. Dialysis studies had shown that most of steady or labelled skin iodine had an iodide form (90 to 95% of the total iodine). There were at least two intracellular iodide pools: the first one was quickly dialysable, in fact about 60 percent of initial radioactivity represented the intracellular iodide equilibrated with extracellular fluid. The other one wasn't or was little dialysable representing probably the cutaneous iodide storage compartment. Chromatography studies (Dowex or Sephadex) demonstrated that the skin of the young and adult rat contained T4 and T3 hormones in a small percentage. The iodide represented a value more than 90% of initial total radioactivity. Results concerning kinetic skin iodine, eight and twenty four hours after LT4(125)I injected to adults and to control and iodine deficient ten day old rats, confirmed those obtained here by Dowex chromatography and previous ones. Triiodothyronine (T3) might have an origin either in thyroid synthesis or in deiodination of T4. Consequently we may say that the skin of the 10 day and 14 day old rats presented a great accumulation of iodide. The perchlorate inhibited this storage. Indeed, in young deficient iodine rats at birth, cutaneous iodide concentrations were reduced whereas those of T4 and T3 as well as the ratio T3/T4 haven't been modified. Therefore the iodine deficiency seemed to have a few effects on the skin deiodinating activity. Indeed the skin of iodine deficient immature rat became unable to accumulate iodide. The main effect of the skin iodine deficiency was the inhibition of iodide transport from the extracellular fluid to the intracellular one, but not inside cellular structures.

Animals↗
PubMed1992

Iodide and T4 kinetics in plasma, thyroid gland and skin of 10-day-old rats: effects of iodine deficiency.

The effects of iodine deficiency on the peripheral metabolism of thyroid hormone in immature rat were evaluated by measuring the kinetics of iodide and thyroxine (T4) in control and iodine-deficient 10-day-old rats. Iodine-deficient pups were obtained by giving the mother drinking water containing perchlorate; this anion is not transferred but prevents iodine transfer in the mother's milk. Labelled iodocompounds were measured in plasma, thyroid and skin for 48 h following intravenous injection of Na131I plus [125I]T4. Data were interpreted by compartmental analysis. The iodide plasma clearance rate, plasma equivalent distribution volume, plasma concentration, production and iodine thyroid content of iodine-deficient rats were significantly lower (-29%, -31%, -84%, -89% and -87% respectively) than in control 10-day-old rats. The iodide thyroid uptake was reduced (-47%) but remained higher than the release of iodine as T4. Cutaneous iodine was lost much more quickly by iodine-deficient pups than by control pups, explaining the decreased iodide distribution volume. The parameters of T4 metabolism were not changed by iodine deficiency, except for a slight but significant reduction of the thyroxinemia and T4 pools (-13%). Thence, T4 production was not significantly changed (about 8 pmol/h in control and iodine-deficient rats). The labelled T4 curves in iodine-deficient and control skin were superimposed and the patterns of labelled T3 derived from [125I]T4 were identical. Thus, the skin of immature rats converts T4 to T3; this process was not disturbed by iodine deficiency. The thyroid function of immature rats is particularly resistant to iodine deficiency, but the mechanisms remain unknown.

Animals↗
PubMed1990

Influence of chronic treatment with iopanoic acid on thyroxine metabolism in the newborn rat.

Parameters of the peripheral metabolism of thyroxine (T4) were studied in the early postnatal period. Iopanoic acid (IOP) was administered to newborn rats that were either euthyroid or rendered hypothyroid in utero by propylthiouracil (PTU) or methimazole (MMI) administration to the mothers during gestation and injected with thyroxine on postnatal days 6 and 7. In euthyroid newborn rats given IOP from postnatal day 6, the plasma T4 level increased (+50%) while the plasma 3,3',5'-triiodothyronine (T3) level slightly decreased (-18%). Peripheral deiodination of T4 was also reduced (about -50%) as estimated by thyroid 125I uptake after injection of 125I (3'-5')L-T4. In the newborn rats rendered hypothyroid in utero and given T4 on postnatal days 6 and 7, IOP treatment started on day 4 decreased the constant rate of elimination (-50%), the distribution volume (-43%) and the metabolic clearance (-74%) of plasma T4. The results were the same in PTU- and MMI-treated newborn rats. The differences between newborn and adult animals under IOP treatment are discussed.

Animals↗
PubMed1982

Thyroxine, triiodothyronine and iodide in different breeds of newborn calves.

Plasma thyroxine (T4), triiodothyronine (T3) and iodide levels were measured from birth until 30 days of age in 17 Holstein x Friesian (HF), 7 Salers and 7 Charolais calves born at term. The response of plasma T4 and T3 levels to bovine thyrotropin (TSH) injection was also compared in two groups of 9 HF calves 3hrs and 21 days, respectively, after birth. In the HF calves, plasma T4 and T3 levels increased from birth to 6 hrs (when the rectal temperature of these calves decreased slightly), then diminished until day 7 and remained stable until 30 days of age. In Salers calves, changes in the plasma T4 and T3 levels were not different from those observed in HF animals. However, in Charolais calves, there was no significant increase in plasma T4 and T3 levels after birth. Twelve and 24 hrs after birth, the plasma iodothyronine levels measured in these animals were lower than in HF calves. In Salers and Charolais calves a positive linear relationship was demonstrated between plasma T4 (or T3) levels at birth and the birth weight. In the three groups of calves, plasma iodide levels decreased from birth until 10 days of age, then remained stable until the end of the first neonatal month. Intravenous injection of the same dose of bovine TSH (5 mU/kg of body weight) induced a rise in the plasma T4 and T3 levels which was significantly more intense in 21-day old calves than in 3-hr old calves.

Aging↗
PubMed1980

Particular aspects of thyroid function development in the postnatal rat with special reference to interrelationships between mother and young.

Previous data have demonstrated that thyroid gland thyroxine secretion rate in suckling rats is high and correlated with the hormonal needs of the young. Non-hormonal iodine metabolism is more elevated in the young than in the adult. The object of the present work was to measure rates of iodine transfer in 10-day old families of rats equilibrated with 125I or not. Reciprocal iodine exchange between mother and young occurred in such a way that the dam recovered about 60 p. 100 of the iodine lost in the milk. Moreover, a large store of extrathyroidal iodine was constituted in the young, particularly in the pelt.

Animal Population Groups↗
PubMed1979

Uptake and metabolism of exogenous and endogenous thyroxine in the brain of young rats.

The uptake of labelled exogenous thyroxine by the brain was determined in 10- and 30-day-old rats. It was three times higher and thyroxine was more deiodinated on day 10 than on day 30. On the other hand, the endogenous hormonal iodine content was estimated in both the brain and the isolated cortical neurones in the young rats of the same ages equilibrated with 125I. On day 10, brain and neurones contained five times more thyroid hormones than on day 30. These results are discussed in the context of the relations previously discovered between development of thyroid function and brain maturation.

Aging↗
PubMed1976

Dynamic study of post-natal thyroid function in the rat.

The thyroid function in development was investigated in post-natal rats. The thyroid iodine content rapidly increased from birth (137 +/- 26 ng iodine/mg thyroid) up to day 10 (338 +/- 42 ng iodine/mg thyroid) then increased more slowly up to day 30 (425 +/- 34 ng iodine/mg thyroid). The maximal plasma concentration of thyroxine was observed on day 16 (56.9 +/- 3.5 ng T4/ml) and of iodide on day 10 (110.2 +/- 12.6 ng I-/ml). The turnover rate constant of extrathyroidal thyroxine was higher at birth (8.0 +/- 2.3 %/h) than at any older age studied (average 6 %/h). Thyroxine secretion by the thyroid was more intense before weaning (37 ng hormonal iodine/h/100 g body weight on days 10 and 20) than after weaning (22 +/- 6 ng hormonal iodine/h/100 g body weight in 30 days old rats). The peripheral deiodination rate of thyroxine represented about 90 % thyroxine secretion rate in newborn and 10 days old rats and only 40% in adult females. In pre-weaning rats, after a single injection of both [131I]L-T4 and [125I]Na, extrathyroidal radioactivity disappeared more slowly than in 30 days old rats and adult animals. This suggests that iodide concentrations of extrathyroidal tissues are higher before than after weaning.

Age Factors↗
PubMedDate not supplied

Relationships between birthweight and plasma thyroxine, triiodothyronine and iodide concentration in lambs.

In crossbred lambs, during the first hours of postnatal life, plasma thyroxine and triiodothyronine concentrations were similar in animals spontaneously born on days 143, 145 or 147 of gestation. However, during the 72 h following delivery, a positive linear relationship was observed between birthweight and plasma T4 or T3 concentrations among the lambs born on day 145. Within 6 h after birth, plasma iodide concentrations reached their highest values, subsequent to the ingestion of iodine from the maternal milk.

Animals↗