Food restriction induced thyroid changes and their reversal after refeeding in female rats and their pups.

In the present study, two groups of pregnant female rats were submitted to food restriction (24 h fast versus 24 h diet intake) from the 14th day of pregnancy until either the 14th day (group B) or the 4th day after parturition (group C). All pups and their mothers were sacrificed on day 14 after delivery. The body weight of the 14-day-old pups (group B) was 46% less than the controls (group A). Free thyroxine and free triiodothyronine levels in the plasma were reduced by 44 and 16% in pups and by 20 and 36% in their mothers, respectively. These reductions were correlated with a decrease in thyroid iodine content of the pups (-50%) and their mothers (-24%). Radioiodine uptake (131I) by the thyroid gland of pups was significantly increased by 27%. Plasma TSH levels were decreased by 38% in pups and by 44% in dams. Morphological changes in thyroid glands were observed in energy restricted dams and in their pups. Some of follicles in pups were empty. Moroever in dams, we noted the presence of peripheral resorbed vacuoles, sign of thyroid hyperactivity. After a refeeding (group C) period of ten days, total recovery occurred in plasma thyroid hormone levels (FT4 and FT3) and in thyroid iodine contents of pups in spite of a partial recovery of body weights and plasma TSH levels. In dams, a partial recovery occurred in plasma thyroid hormone levels in spite of total recovery in thyroid iodine contents, while plasma TSH levels exceeded control values. A significant amelioration in thyroid histological aspects was observed in pups and their dams.

Dimethoate effects on thyroid function in suckling rats.

The aim of our work is to study dimethoate effects on thyroid function given in drinking water (40 mg/kg body weight, equivalent to 0.2 g/L) to mothers from day zero until the 10th day after delivery. Pups and their mothers were sacrificed on day ten after parturition. Compared to a control group, dimethoate-treated pups showed a 48% decrease in body weight which could be attributed to a defect in thyroid hormones. Indeed, after treatment by dimethoate, plasma rates of free T4 and T3 decreased by 56% and 40% in the young and by 27% and 15% in dams respectively. We can attribute the reduction in plasma thyroxine and triiodothyronine rates to a decrease in thyroid iodine levels (-75%) in the young and (-24%) in their mothers. The decrease in production of thyroid hormones after dimethoate treatment affect thyroid stimulating hormone (TSH) levels. In fact, plasma TSH levels were multiplied in dimethoate-treated group by factors of 2.31 in dams and 1.96 in their offspring. These biochemical modifications confirmed the histological thyroid aspects of pups and dams. In fact, in dimethoate-treated rats, some thyroid follicles of pups presented vesicular cavities without colloid; others contained colloid. However in dams, thyroid follicles presented cubical epithelial cells which surrounded empty vesicular cavities.

[Induction and reversibility of thyroid proliferative changes in suckling rats given thiocyanate]. / Induction et réversibilité d'action du thiocyanate sur la fonction thyroïdienne chez le rat en période d'allaitement.

Potassium thiocyanate given in the drinking water of pregnant rats led to decreased body weight in their 14-day-old offspring (27%) without altering thyroid weight. Reduction of the suckling rat's body weight could be explained be defective thyroxinemia (38). Plasma FT3 and TSH were unchanged after thiocyanate treatment. The biochemical changes were in agreement with the histological aspects of the hypothyroid animals. The typical pattern was hyperplastic goiter. Colloid volume was reduced compared with controls. Presence of resorbed peripheral vacuoles, a sign of thyroid hyperactivity, was disclosed by a three-fold increase in radioiodide (131I) uptake compared with controls. When the antithyroid drug was removed from the mother's milk, the pups'weight increased but did not reach control values. Plasma thyroid hormone levels returned to normal and even exceeded control values in spite of partial recovery of thyroid iodine content when thiocyanate treatment was stopped for ten days.

[Thiocyanate and central nervous system maturation of young mice]. / Effets du thiocyanate sur la fonction thyroïdienne et la maturation du système nerveux central de la jeune souris.

Potassium thiocyanate, given to the drink of pregnant mothers provoked a body weight decrease of 14 day-old mice (-18%), without perturbations of cerebrum and cerebellum weights. The reduction of pups' body weight could be explained by a decrease of plasmatic thyroid hormone levels: FT3 and FT4, (-54; -57%) in youngs and (-66; -49%) in their mothers. A defect of thyroid hormone levels, observed in young mice, provoked a decrease of cerebrum and cerebellum protein concentrations (-15 and -13%) respectively. Modifications of biochemical parameters confirmed the histological aspects of hypothyroid mice cerebellum with purkinje cells incompletely differentiated. When thiocyanate ion was removed from mothers' drink, we have noted in pups a partial return of some biochemical parameters (iodine thyroid contents, protein concentrations of cerebrum and cerebellum) and of cerebellum histological aspects. While thyroxinemia (FT4) and plasmatic FT3 levels were completely restored and even exceeded control values, which were necessary for central nervous system maturity of young.

[Propythiouracil and perchlorate effects on thyroid function in young and lactating mice]. / Effets de deux antithyroïdiens de synthèse (propylthiouracile et perchlorate) sur la fonction thyroïdienne de la souris en période d'allaitement.

We have studied the effects of propythiouracil (PTU) or perchlorate (CIO(4)(-)), given to the mothers' drink from the 15(th) day of pregnancy until the day of sacrifice, on thyroid function of suckling mice. Antihyroid drugs (PTU or CIO(4)(-)) provoked growth perturbations of young mice during studied ages from 6 to 18 days. A decrease of body weight was respectively as follows: 14 and 22% in 6 day-old mice; 16 and 23% in 10 day-old mice; 18 and 18% in 14 day-old mice; 19 and 11% in 18 day-old mice. We have noticed an hypertrophy of thyroid glands of pups and their mothers caused by an increase of pituitary TSH. Thyroid follicles presented the aspect of hypothyroid animals with an increase of follicular number and vascularisation. Structural modifications confirmed biochemical results. In fact thyroid iodine contents decreased strongly in young as follow: 40 and 43% in 6 day-old mice; 51 and 50% in 10 day-old mice; 66 and 84% in 14 day-old mice; 54 and 89% at 18 day-old mice and in their mothers (50, 37%; 59, 54%; 75, 65% and 85, 72%) respectively after PTU or CIO(4)(-) treatment. A decrease of iodine thyroid gland was accompanied by an important fall of free thyroid hormones levels (FT3 and FT4) in young and adult mice. A decrease of thyroid hormonemia could explain the pups' growth perturbations.