Thyroid physiology during the postnatal period in the rat: A study of the development of thyroid function and of the morphogenetic effects of thyroxine with special reference to cerebellar maturation

Clos, J.; Crépel, F.; Legrand, C; Legrand, J.; Rabié, A.; Vigouroux, E.

doi:10.1016/0016-6480(74)90127-0

Cited by 94 publications

(41 citation statements)

References 24 publications

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“…In most cases, new-born suckling rats were made hypothyroid by administering propylthiouracil (PTU: Sigma; 50 mg per day) to their mothers from day 18 of gestation via gastric intubation (Clos et al 1974). However, in some cases, hypothyroidism was induced in new-born rats by destroying their thyroid glands with radioactive iodine (Geel & Timiras, 1967); pregnant rats were fed on a low iodine diet (Oriental; 0-11 #ug iodine/g) which was continued until the offspring were 6 days old.…”

Section: Preparationmentioning

confidence: 99%

Altered developmental changes of neuromuscular junction in hypo‐ and hyperthyroid rats

Kawakami

Obata

1982

The Journal of Physiology

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SUMMARY1. Effects of thyroid hormone on the development of neuromuscular junctions (n.m.j.s.) were investigated electrophysiologically in the diaphragms (sternal region) of normal, hypo-and hyperthyroid rats from the age of birth (day 0) to day 35.2. Hypothyroidism in new-born rats was induced either by daily administration of propylthiouracil to mothers or by subcutaneous injection of 150 1sCi l311 on day 1. Hyperthyroidism was induced by daily injection of thyroxine.3. In normal rats up to day 10, muscle fibres were innervated polyneuronally. By day 20, multiple innervation was eliminated and muscle fibres received only a single input. In hypothyroid rats elimination of polyneuronal innervation was retarded by 5-8 days, while in hyperthyroid rats the elimination was accelerated by 2-3 days.4. The frequency of miniature end-plate potentials (m.e.p.p.s) in normal rats increased from one per 40 sec on days 0-5 to 1/sec on days 25-35. The m.e.p.p. frequency in hypothyroid rats was 25-65 % of that in normal rats of the same age.In hyperthyroid rats the m.e.p.p. frequency was normal up to day 18 but subnormal afterwards. The duration ofm.e.p.p. measured on day 22-23 was slower in hypothyroid rats and faster in hyperthyroid rats, relative to m.e.p.ps in normal rats.5. The sensitivity to acetylcholine (ACh) at extrajunctional regions in normal rats was about 100 mV/nC at birth and declined to 1 mV/nC by day 26. In hypothyroid rats, the ACh sensitivity was as high as 30 mV/nC on day 26; in hyperthyroid rats, ACh sensitivity on day 26 was undetectable.6. With pairs of nerve stimuli (applied at a 50 msec interval), the second end-plate potential was facilitated until day 10 and depressed after day 16 in normal rats. This shift from facilitation to depression during development was not altered in either hypoor hyperthyroid rats.7. It is concluded that the lack and excess of thyroid hormone retards and facilitates the development of n.m.j.s. respectively. Possible mechanisms for this altered development are discussed.

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Section: Preparationmentioning

confidence: 99%

Altered developmental changes of neuromuscular junction in hypo‐ and hyperthyroid rats

Kawakami

Obata

1982

The Journal of Physiology

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“…However, when the cytoplas- mic receptors for glucocorticoids in the jejunum were assayed throughout the developmental period they were found to be present in higher concentrations during the first and second postnatal week than during the third week (71), thus failing to provide a basis for increasing responsiveness. Since circulating concentrations of thyroxine are known to increase considerably between postnatal days 10 and 16 (72)(73)(74)(75) we have investigated the possibility that this hormone synergizes with glucocorticoids and thereby explains the timing of the glucocorticoid-mediated changes in the intestine (76). The data indicate that thyroxine plays no role in the timing of the developmental appearance of sucrase activity, although it does have an important permissive effect in determining the slope of the developmental rise of sucrase activity.…”

Section: Role Of Hormonesmentioning

confidence: 99%

Biochemistry of Intestinal Development

Henning¹

1979

Environmental Health Perspectives

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In biochemical terms, the rat small intestine is relatively immature at birth and for the first two postnatal weeks. Then during the third week a dramatic array ofenzymic changes begins, and by the end ofthe fourth week the intestine has the digestive and absorptive properties of the adult. Selective examples of these changes are discussed with emphasis on their implications for toxicological studies. The review also includes a detailed consideration of the roles of the dietary change of weaning and of glucocorticoid and thyroid hormones in the regulation of intestinal development.My aim in this paper is to use the rat as a model system for a discussion of the postnatal development of small intestinal function. Factors which affect the developmental process will be reviewed in terms of their implications for toxicological studies. Morphologic Development of the IntestineBy the time of birth, the intestinal mucosa of the rat displays a high level of structural development characterized by villi lined with a single layer of columnar epithelial cells which have well-defined microvilli at their absorptive surface (1-3). After birth, continuous proliferation of epithelial cells occurs only in the lower regions of the crypts (4, 5), and cells migrate from there onto and along the villi, eventually being extruded from the tips into the lumen of the intestine. In adult rats and mice the generation time for the crypt cells is 10-14 hr (6), and the transit time along the length of the villus is approximately 48 hr (7). The characteristics of proliferation and migration of enterocytes in adult animals are dealt with in detail in the review by Lipkin (8). In neonatal rats, generation and migration of the cells is much slower than in adults. Despite the fact that the neonatal villi are shorter, the transit time is at least % hr (7, 9). During the third postnatal week there are significant changes in both cell kinetics and mor-

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“…The thyroxine secretion rate (TSR) in rats is high during the first two postnatal weeks (Vigouroux, 1976 ;Fisher et al, 1977). An excellent correlation has been established between the TSR and the thyroxine needs for normal maturation (Clos et al, 1974 ; Vigouroux, Clos and Legrand, 1979). Contrary to adult rats, the non-hormonal iodine metabolism in suckling rats quantitatively overlaps that of the thyroid hormones (Stolc, Knopp and Stolcova, 1973 ;Vigouroux, 1976) Clos and Legrand (1979).…”

Section: Introductionmentioning

confidence: 97%

“…From postnatal week 3, the suckling rat progressively replaces the dam's milk, which has a high iodine content (Vigouroux, Rostaqui and Fenerole, 1978), by an iodine-pcor diet. This occurs while thyroxine secretion rate is still intense (Clos et al, 1974 ;Vigouroux, 1976). The thyroid of the pups may use the iodine accumulated in the pelt and other organs.…”

Section: Introductionmentioning

confidence: 99%

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

Vigouroux¹,

Rostaqui²

1980

Reprod. Nutr. Dévelop.

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Summary. 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 125 1 or not. Reciprocal iodine exchange between mother and yound 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.Introduction.

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Thyroid physiology during the postnatal period in the rat: A study of the development of thyroid function and of the morphogenetic effects of thyroxine with special reference to cerebellar maturation

Cited by 94 publications

References 24 publications

Altered developmental changes of neuromuscular junction in hypo‐ and hyperthyroid rats

Altered developmental changes of neuromuscular junction in hypo‐ and hyperthyroid rats

Biochemistry of Intestinal Development

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

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