Effects of casein on iodine metabolism in body and thyroid of mice under excessive iodine

Abstract

Objective To observe the effects of casein on iodine metabolism in blood,urine and thyroid of mice under excessive iodine.Methods A 2 by 3 factorial design was used in the experiment.The levels of iodine and casein were 50 and 600 μg/L in drinking water and 0( Ⅰ ),10％( Ⅱ ),20％( m ) in food,respectively.After six and twelve months,iodine content in serum,thyroid gland and urine was determined by arsenic-cerium catalyzed spectrophotometry.Results In six months,the levels of serum iodine in 50 Ⅰ,50 Ⅱ,50Ⅲ,600 Ⅰ,600 Ⅱ,and 600Ⅲ groups were (85.59 ± 8.78),(64.59 ± 9.06),(72.53 ± 11.69),(110.04 ± 9.37),(81.06 ± 9.94),(86.63 ± 19.59)μg/L,respectively; the levels of iodine content in thyroid gland were (0.21 ± 0.09),(0.29 ±0.08),(0.24 ± 0.05),(0.50 ± 0.10),(0.37 ± 0.13),(0.42 ± 0.12)g/kg,respectively; the levels of urinary iodine median were 87.5,68.1,105.5,746.5,828.3,1014.2 μg/L,respectively.The variance analysis results of factorial design showed iodine and casein significantly influenced the serum iodine level(F =27.95,18.52,all P ＜0.05),however,there was no interaction between the two(F =0.81,P ＞ 0.05); iodine significantly influenced the iodine content in thyroid gland(F =31.35,P ＜ 0.05),the presence of iodine interacted with casein(F =3.34,P ＜0.05).In twelve months,the levels of serum iodine were (88.54 ± 12.33),(72.45 ± 7.73),(72.93 ± 13.61),( 106.26 ± 12.00),(90.03 ± 7.90),( 104.88 ± 11.67)μg/L,respectively; the levels of iodine content in thyroid gland were (0.58 ± 0.12),(0.40 ± 0.14),(0.69 ± 0.16),(0.84 ± 0.13),(0.89 ± 0.13),(1.02 ± 0.11 )g/kg,respectively;the levels of urinary iodine median were 104.8,121.5,102.7,829.1,1080.8,895.2 μg/L,respectively.The variance analysis results of factorial design showed iodine and casein significantly influenced the iodine content in serum and thyroid gland (F =42.78,7.42 and 66.62,7.90,all P ＜ 0.05),however,there was no interaction between the two(F =1.93,2.31,all P ＞ 0.05).Conclusions Long-term intake of iodine can significantly increase the iodine content in serum,thyroid gland and urine,but casein may accelerate iodine excretion and partly reduce the effect. Key words: Iodine;  Caseins;  Thyroid