Individual variation in response to simulated hypoxic stress of rats.

With an aim to categorize the animals exposed to simulated hypobaric hypoxia and to evaluate the hormonal profile responsible for individual variation in response to hypoxic stress, degree of tolerance to hypobaric hypoxia was measured by exposing the animals to a simulated altitude of 10,668 m at 32 °C and animals were categorized as low and high tolerant groups based on their gasping time. The hormonal profiles of these groups were evaluated just after exposure to the test. The results showed a distinct individual difference in response to hypoxic tolerance test. There was a significant increase in plasma norepinephrine concentration in high tolerant group than low tolerant rats. After hypoxic tolerance test, total circulating corticosterone (CORT) level also increased but this was not significant in high tolerant rats as compared to low tolerant rats. Corticosteroid binding globulin (CBG) concentration differ significantly between high and low tolerant groups of rats resulting in significant changes in circulating free corticosterone that in turn may be responsible for individual differences in hypoxic gasping time. Significant differences were also observed in prolactin and testosterone levels of both the groups. The results established the method of differentiating the animals according their response to hypoxic tolerance test. These data indicate that multiple components rather than only plasma glucocorticoid of the stress response are providing a basis for individual differences in physiological responses to hypoxic stress.

Bioavailability of iodine and hardness (magnesium and calcium salt) in drinking water in the etiology of endemic goitre in Sundarban delta of West Bengal (India).

Endemic goitre has been reported from the ecologically diverse Sundarban delta of West Bengal (India). To study the etiological factors for the persistence of endemic goitre, bioavailability of iodine and hardness of water used for drinking in the region were evaluated because these common environmental factors are inversely and directly related with goitre prevalence in several geographical regions. For the present study from 19 Community Development Blocks of Sundarban delta, 19 areas were selected at random. From each area at least 8 drinking water samples were collected and analyzed for iodine and the hardness (calcium and magnesium salt content). Iodine content in the drinking water samples was found in the range from 21 to 119 mg/L and total hardness of drinking water was found to range from 50 to 480 ppm. Presence of magnesium salt was found higher than the calcium salts in most of the samples. These findings suggest that the entire delta region is environmentally iodine sufficient but water is relatively hard and thus possibility of hardness of water for the persistence of endemic goitre may not be ruled out.

Effect of radish (Raphanus sativus Linn.) on thyroid status under conditions of varying iodine intake in rats.

Cruciferous plants viz. cabbage, cauliflower, turnip, radish, mustard etc. that contain goitrogenic/antithyroid substances, constitute a portion of regular human diet. The effect of chronic feeding of fresh and cooked radish, R. sativus under varying state of iodine intake on morphological and functional status of thyroid in albino rats was evaluated by thyroid gland morphology and histology, thyroid peroxidase activity, serum triiodothyronine, thyroxine and thyrotropin levels. The consumption pattern of iodine and goitrogens of cyanogenic origin was evaluated by measuring urinary iodine and thiocyanate levels respectively. After chronic radish feeding, increased weight of thyroid gland, decreased thyroid peroxidase activity, reduced thyroid hormone profiles and elevated level of thyrotropin were observed resembling a relative state of hypoactive thyroid gland in comparison to control even after supplementation of adequate iodine.

Iodine nutritional status & prevalence of goitre in Sundarban delta of South 24-Parganas, West Bengal.

BACKGROUND & OBJECTIVE: In post salt iodization phase endemic goitre and associated iodine deficiency disorders (IDD) were found prevalent in a randomly selected rural area of Sundarban delta and its adjoining areas of West Bengal. The present investigation was thus undertaken to study the total goitre rate, urinary iodine and thiocyanate excretion pattern of the school going children, iodine content in edible salt and drinking water in the Sundarban delta of South 24-Parganas in West Bengal. METHODS: A total of 4656 school children (6-12 yr) were clinically examined for goitre from 13 different areas in the delta region. Urinary iodine and thiocyanate levels were measured in 520 (40 from each area) samples collected randomly to evaluate the iodine nutritional status and consumption pattern of dietary goitrogen. Simultaneously iodine content was determined in 104 (8 from each area) drinking water samples and 455 (35 from each area) edible salt samples collected from the areas. RESULTS: Children of all the areas were affected by endemic goitre. The prevalence rates were in the ranges from 25-61 per cent; overall goitre prevalence was 38.2 per cent (grade 1--34.0%; grade 2--4.2%). Median urinary iodine level in the studied areas was 225 microg/l (range 115-525 microg/l) indicating no biochemical iodine deficiency in the region. Mean urinary thiocyanate levels were in the range from 0.326-1.004 mg/dl. Iodine content in drinking water samples were in the ranges from 22-119 microg/l, and 55.6 per cent edible salt samples had iodine level above the recommended 15 ppm at the consumption point. INTERPRETATION & CONCLUSION: The severity of endemic goitre was high in the studied population though the iodine nutritional status was found satisfactory in the region indicating no biochemical iodine deficiency. The people of the region consumed iodine through iodized salt but about 44 per cent of the salt samples at household level contained inadequate iodine, however their iodine intake was compensated through iodine in water and food. They also consumed dietary goitrogen. Environmental factors other than iodine deficiency may have possible role for the persistence of endemic goitre in the region. More investigations are thus necessary to arrive at certain definite cause of high goitre rates in this population.

Evaluation of possible goitrogenic and anti-thyroidal effect of nitrate, a potential environmental pollutant.

Nitrate is a wide spread contaminant of ground and surface water. The source of nitrate in the ground water may be from run off or seepage from fertilized soil, municipal or industrial waste water, land fills, septic system, urban drainage or decaying plants. Human and animal systems are affected severely on nitrate exposure. The study was to investigate the effect of dietary nitrate exposure on the thyroid status along with the state of iodine nutrition. Rats were fed diet containing 3% potassium nitrate (KNO3) for 4 weeks and then thyroid status was evaluated by thyroid gland weight, urinary iodine excretion pattern, thyroid peroxidase (TPO) activity, serum levels of total thyroxine (T4), triiodothyronine (T3) and thyroid stimulating hormone (TSH) concentrations. In nitrate treated animals, the weight of thyroid gland was increased significantly (P<0.001) while thyroid peroxidase activity (P<0.01), serum T4 (P<0.01) and serum T3 levels (P<0.001) were reduced; but serum TSH level was increased (P<0.001) along with slightly elevated iodine excretion level (P<0.001) in comparison to control animals. The overall results indicated the development of a relative state of functional hypothyroidism with enlarged thyroid after nitrate exposure. This study can explain a part for the persistence of residual goitre in the post-salt iodization phase.

Effect of bamboo shoot, Bambusa arundinacea (Retz.) Willd. on thyroid status under conditions of varying iodine intake in rats.

Young shoots or sprouts of common bamboos are used as food in third world countries. Evidences suggest the presence of cyanogenic glucoside like anti-thyroidal substance in bamboo shoots (BS) but effect of prolonged BS consumption on thyroid status under conditions of varying iodine nutriture remains unexplored. The study was undertaken to evaluate goitrogenic content, in vitro anti thyroid peroxidase (TPO) activity and in vivo anti thyroid potential of BS with and without extra iodide. Fresh BS contains high cyanogenic glucoside (551 mg/kg), followed by thiocyanate (24mg/kg) and glucosinolate (9.57mg/kg). In vitro inhibition in TPO activity was found with raw, raw boiled and cooked extracts. Inhibition constant (IC50) and PTU equivalence of fresh BS were 27.5+/-0.77 microg and 3.27 respectively. Extra iodide in the incubation media reduced TPO inhibition induced by BS but could not cancel it. Thyroid weight, TPO activity and total serum thyroid hormone levels of BS fed animals for 45 and 90 days respectively were determined and compared with controls. Significant increase in thyroid weight as well as higher excretion of thiocyanate and iodine along with marked decrease in thyroid peroxidase activity, T4 and T3 levels were observed in BS fed group. Chronic BS consumption gradually developed a state of hypothyroidism. Extra iodide had reduced the anti-thyroidal effect of BS to an extent but could not cancel it because of excessive cyanogenic glucoside, glucosinolate and thiocyanate present in it.