potassium-thiocyanate and Hypothyroidism

Iodine deficiency disorders affect reproductive performance in the afflicted populations. Environmental iodine deficiency (ID) and goitrogens are important in their aetiology. We observed earlier that chronic maternal dietary ID but not goitrogen feeding altered the blood-brain barrier nutrient transport in adult rats. Whether similar differences exist in their effects on reproduction of dams and postnatal performance of the offspring has been assessed. Inbred, female, weaning WNIN rats were rendered hypothyroid by feeding for 8-12 weeks, a low iodine test diet or a control diet with added potassium thiocyanate (KSCN) (@ 25 mg/rat/day). Following mating with control males, they continued on their respective diets till their pups were weaned. Indices of reproductive performance such as percentage of conception, mortality of dams during pregnancy and parturition, litter size, and survival of pups till weaning were affected markedly by ID but not thiocyanate feeding. Neither ID nor thiocyanate feeding from conception or parturition affected their reproductive performance. Nevertheless, postnatal weight gain of pups was less in all the three ID groups but not thiocyanate fed dams. Rehabilitation of chronically ID pregnant dams from conception or parturition did not improve their pregnancy weight gain, litter size or birth weight of pups but decreased abortion and mortality of mothers during pregnancy and parturition. Rehabilitation improved the pups' postnatal weight gain but the effect was only moderate. Based on the results of the present study it may be suggested that maternal ID but not thiocyanate feeding affects reproductive performance and postnatal performance of their offspring.

Topics: Animal Feed; Animals; Antithyroid Agents; Birth Weight; Female; Hypothyroidism; Iodine; Litter Size; Maternal Exposure; Mothers; Pregnancy; Pregnancy, Animal; Rats; Thiocyanates

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.

Topics: Animals; Animals, Suckling; Antithyroid Agents; Body Weight; Female; Gestational Age; Goiter; Hypothyroidism; Iodine; Maternal-Fetal Exchange; Pregnancy; Rats; Thiocyanates; Thyroid Gland; Thyrotropin; Thyroxine

Populations living in goitre endemic areas consume foods rich in a variety of goitrogens of different potencies and some are severely hypothyroid. Recently we observed in Wistar/NIN rats that chronic feeding of KSCN to dams produced only a moderate hypothyroidism and decreased the transport of 2-deoxy-D-glucose (2-DG) across the blood-brain barrier (BBB) in the offspring. The present studies were conducted to assess whether severe hypothyroidism would have greater effect on BBB nutrient transport. It has now been observed that weaning the pups of KSCN fed dams on to KSCN diet for four weeks had no further effect either on their thyroid status or the BBB 2-DG transport. However, feeding KSCN to rats through two generations produced somewhat severe hypothyroidism in F2 pups than that in F1 pups. Interestingly, unlike in F1 pups, the BBB transport of all the three nutrients tested (2-DG, Leu and Tyr) was significantly decreased in F2 pups, albeit to a small extent (10-15%). On the other hand the potent goitrogen: methyl mercaptoimidazole (MMI) even on short term feeding to pregnant dams produced very severe hypothyroidism in the offspring [Serum T4:0.55+/-0.09 microg/dl vs 4.96+/-0.85 in controls]. Surprisingly, the BBB transport of 2-DG, Leu, Tyr and also sucrose, the background marker, was significantly increased in these pups (20-30%). The diverse effects of goitrogen-induced moderate and severe hypothyroidism observed here on the BBB nutrient transport probably suggest different mechanisms for iodine deficiency disorders of different aetiologies and hence the need for discrete approaches for their management.

Topics: Animals; Antithyroid Agents; Blood-Brain Barrier; Deoxyglucose; Female; Hypothyroidism; Leucine; Methimazole; Pregnancy; Rats; Rats, Wistar; Sucrose; Thiocyanates; Tyrosine

The effects of feeding thiocyanate (a goitrogen derived from thioglucosides, which are naturally occurring in certain foods) to female rats throughout gestation and lactation on a microtubule assembly of pups during postnatal development were examined. Microtubules, which are important components of the neuronal cell cytoskeleton, may serve as markers of neurite growth. A progressive increase with age in the initial rate of microtubule assembly was apparent in both untreated control and thiocyanate-treated rat pups in the cerebrum, cerebellum and brainstem. Thiocyanate treatment did not alter the tubulin content at any of the developmental stages studied (7, 14 and 21 days postnatal). However, examination of the microtubule assembly revealed a markedly reduced polymerization of tubulin into microtubules in brain regions of thiocyanate-treated rats compared with untreated controls. The effect of thiocyanate on microtubule assembly was evident at all three ages (7, 14 and 21 days). Thiocyanate-induced hypothyroidism increased the lag period for initiation of assembly and also altered the initial rate of microtubule formation. This study suggests that a partial suppression of thyroid function by thiocyanate, as evidenced by a decrease in circulating concentrations of thyroxine, could bring about alterations in microtubule formation during brain development and suggests the possibility of an impairment in the process of microtubule metabolism.

Topics: Analysis of Variance; Animals; Brain; Diet; Female; Hypothyroidism; Microtubules; Rats; Rats, Wistar; Thiocyanates; Thyroxine; Triiodothyronine; Tubulin