A study of the efficacy of L-3,5-diiodotyrosine and inorganic iodine in iodine-deficiency Wistar rats / 中华地方病学杂志

ABSTRACT

Objective To study the efficacy of L-3,5-diiodotyrosine (DIT) and inorganic iodine (KIO3) in iodine-deficiency Wistar rats.Methods Sixty Wistar rats,weighting about 160-180 g,were divided into two groups according to body weight by the random number table method:iodine-deficiency model (40 rats) was fed with low-iodine food (the iodine content was 35.9 μg/kg);optimal-iodine model (20 rats) was fed with low-iodine food and given with KIO3 water (the iodine content was 18 mg/L) 0.5 ml by intragastric once a day.Model was established for 3 months.Iodine-deficiency model was subdivided into low iodine (LI) group,KIO3 group and DIT group,eight,nine,ten rats in each group;from optimal-iodine model,nine rats were randomly selected as optimal iodine (NI) group.LI group was fed with low-iodine food;KIO3 group was fed with low-iodine food and given with KIO3 water (the iodine content was 18 mg/L) 0.5 ml by intragastric once a day;DIT group was fed with low-iodine food and given with DIT water (the iodine content was 18 mg/L) 0.5 ml by intragastric once a day;NI group was fed with low-iodine food and given with KIO3 water (the iodine content was 18 mg/L) 0.5 ml by intragastric once a day.After 3 months,24-hour urine of the rats was collected.According to the method for determination of iodine in urine by As3 +-Ce4+ catalytic spectrophotometry (WS/T 107-2006),iodine content in urine was detected.Rats were anesthetized intraperitoneally with 25％ urethane,blood from abdominal aortic was collected to determinate the serum thyroid hormone [total triiodothyronine (TT3),total thyroxine (TT4),free triiodothyronine (FT3),free thyroxine (FT4)] level in rats by automatic electrochemical luminescence immunoassay.All the rats were sacrificed to analyze the thyroid weight.Results ① The urine iodine showed significant differences in the four groups (x2 =25.24,P ＜ 0.05).The median of urine iodine concentration in the LI,NI,KIO3 and DIT groups were 3.00,286.14,223.37,214.33 μg/L,respectively.The urine iodine concentration in LI group was significantly lower than those of other three groups (all P ＜ 0.05).② The serum TT3,TT4,FT3,FT4 levels showed significant differences in the four groups (F =63.48,140.73,130.20,365.27,all P ＜ 0.05).And the hormone levels in KIO3 group were lower than those of the DIT group [TT3(1.57 ± 0.20) vs.(1.97 ± 0.18) mmol/L,TT4(51.23 ± 4.90) vs.(71.94 ± 5.27) mmol/L,FT3(5.34 ± 0.45) vs.(6.98 ± 0.33) pmol/L,FT4(26.18 ± 2.30) vs.(35.47 ± 2.28) pmol/L,all P ＜ 0.05].③The color of thyroid in KIO3 and DIT groups became pale pink.The absolute and relative thyroid weight showed significant differences in the four groups (F =225.05,345.40,all P ＜ 0.05).The absolute thyroid weight [(31.76 ± 1.75) mg] and relative thyroid weight [(11.69 ± 3.47) mg/100 g] in DIT group was lower than that of the KIO3 group [(36.31 ± 5.23) mg,(12.83 ± 4.38) mg/100 g,all P ＜ 0.05].Conclusion Animal experimental results show that DIT has a better iodine-supplementing efficacy than that of KIO3.