ABSTRACT
Objective Take alkaline ashing method as golden standard to explore the accuracy of chloric acid digestion method in determination of human milk iodine. Methods Sixty one breast milk samples collected in Hexi district of Tianjin was measured by the method for determination of iodine in foodstuff by As3+-Ce4+ catalytic spectrophotometry (referred to as the alkaline ashing method) published in 2008 and the method for determination of iodine in urine by As3+-Ce4+ catalytic spectrophotometry(referred to as acid digestion) published in 1999, respectively. were highly correlated(r = 0.960, t = 26.3, P < 0.01), and the regression equation was (Y) = - 28.1 + 0.808X, in which X was independent variable, that is the results of alkaline ashing method; (Y) was dependent variable, that is the estimated data of chloric acid digestion method. The average difference of the results measured by the two methods was 68.3 μg/L, and the results from chloric acid digestion was 38.9% which lower than that of alkaline samples were diluted by 3,4 and 5-fold and then digested by chloric acid, the liquid clarification rates were 80.3% ashing and chloric acid digestion method were, respectively, 165.4, 110.0 μg/L. Conclusions Compared with alkaline ashing method, the results determined by chloric acid digestion method are significantly lower. It is suggested that there are systemic errors in chloric acid digestion method, which means that alkaline ashing method can not be replaced by the chloric acid digestion method.
ABSTRACT
Objective To study the expression level of thyroid insulin-like growth factor-Ⅰ (IGF-Ⅰ) in iodine deficiency and excess mice and the effect of thyroid gland IGF-Ⅰ in the thyroid morphological change. Methods Forty-eight Balb/c mice were chosen as studied objects,weighing about 16 g. They were divided into three groups: low iodine(LI,iodine content of 50 μg/kg in feed,drinking deironized water) group,normoi(NI,iodine content of 300 μg/kg in feed,drinking deironized water) group and high(HI,iodine content of 300 μg/kg in feed,iodoine of content 14 700 μg/kg in drinking) group,16 mice in each group. Mice were put to death after 12 weeks and taken out of their thyroid gland. The body weight,absolute and relative weights of thyroid gland were measured and the morphological change of thyroid gland were observed under microscope. The expression levels of thyroid gland IGF-Ⅰ mRNA and protein were detected by RT-PCR and immunohistochemistry,respectively. Results There were statistical significances between groups of thyroid absolute and relative weights(F = 315.881,405.921,all P < 0.01). LI group [(10.71±4.03) mg,(44.98±15.39)mg/100 g body weight]and HI group [(3.42±1.17)mg,(13.50± 3.89)mg/100 g body weight]had heavier thyroid absolute and relative weights than NI group[(2.11±0.53)mg,(8.35±1.98)mg/100 g body weight,all P < 0.01]. Under microscopy,the thyroid follicle capacity grew down and the follicle quantity grew up in LI group,the epithelium was stylolitic,the colloid diminished or absence in follicular cavity,while HI group presented colloid accumulation without follicular hyperplasia. The expression level of thyroid gland IGF-Ⅰ mRNA in LI group(1.03±0.32) was more than that in NI(0.65±0.19) and HI(0.59± 0.20) groups(F= 7.518,P< 0.01). In contrast to NI,there was no difference in the expression level of thyroid gland IGF-Ⅰ mRNA in HI group(P > 0.05). The brownish particles of LI group were more than NI and HI groups in the thyroid follicle epithelium by immunohistochemistry,while HI group was less than NI group. Conclusions The mice of iodine deficiency presented follicular hyperplasia goiter,the mice of iodine excess presented colloid accumulative goiter. The change of IGF-Ⅰ mRNA and protein expression may participate morphologleal change,indicating autocrine IGF-Ⅰ of thyroid gland may play an important role in regulating goiter formation.
ABSTRACT
Objective To study effect of excessive iodine intake on sodium-iodide symporter(NIS)mRNA and protein expression of breast in lactating rats.Methods60 Wistar rats,having been weaned for one month,were randomly divided into three groups according to their body weights,I.e,①normal iodine(NI,30 rats);②ten fold high iodine(10 HI,15 rats);③one hundred fold high iodine(100 HI,15 rats).Eating food containing iodine of 300μg/L and drinking water of iodine at 5,1845,20 295μg/L,respectively.After fed for 3 months,the rats mated and had offspring,and urine and milk iodine of lactating rats were determined by As-Ce-catalytic spectrophotometric method.Their marmnary glands were sampled at lactation day 10.Then NIS mRNA expression by RT-PCR was determined and NIS protein by immunohistochemistry(SABC)was observed.Results The urine iodine of 10 HI group(3597.5μg/L)and 100HI group(25 404.3μg/L)increased obviously compared with that of NI group(344.7μg/L).The milk iodine of 10HI group(27.1×103μg/L)and 100HI group(191.0×1μg/L)was higher than that of NI group(6.0×103μg/L),but the increased fold of milk iodine was not paralleled with that of urine iodine.Difference of NIS mRNA expression was significant(F=24.19,P＜0.01)among the groups,and the NIS mRNA expression in 10HI(1.250±0.034)and 100HI(1.272±0.039)group were less than that in NI (1.532±0.044)group(P＜0.01).The breast NIS mRNA expression in lactating rats(1.532±0.044)was significantly higher than that in unlactating rats(0.879±0.018,P＜0.01).With the increasing iodine uptake,NIS protein expression decreased.Conclusions The NIS mRNA and protein in rat breasts is down-regulated by excessive iodine intake.So increasing extent of milk iodine concentration is inhibited,which is important to prevent off-spring from getting excessive iodine intake from parental generation.