title: [Overdose of iodine on expression of CCK gene in rat brains].
abstract: OBJECTIVE
  To observe the effect of overdose iodine on the expression of CCK gene in brains of rats and identify the possible mechanisms.
  
  
  METHODS
  One-month weaning Wistar rats were randomly divided into five groups which were fed with normal feedstuff and water supplemented with different concentrations of potassium iodide, named A group (iodine ration was about 6.15 microg per day), B group (iodine ration was about 30.75 microg per day), C group (iodine ration was about 61.5 microg per day), D group (iodine ration was about 307.5 microg per day) and E group (iodine ration was about 615 microg per day). Rats were sacrificed after being fed for three or six months. Then serum thyroid hormones were measured by radioimmunoassay and the mRNA level of CCK gene was studied by using RT-PCR technique.
  
  
  RESULTS
  At the end of three months, the values of thyroid hormones in E group [TT4 (45.2 +/- 13.7) nmol/L, TI'3 (0.65 +/- 0.20) nmol/L, FT3 (0.93 +/- 0.45) pmol/L, FT4 (7.07 +/- 2.43) pmol/L, rT3 (0.15 +/- 0.04) nmol/L] were all lower than those in A group [TT4 (76.0 +/- 18.8) nmol/L, TT3 (1.34 +/- 0.41) nmol/L, FT3 (2.45 +/- 0.62) pmol/L, FT4 (15.12 +/- 3.40) pmol/L, rT3 (0.24 +/- 0.04) nmol/L]. There were significant differences between E group and A group on the levels of serum TH (F values are 14.68, 16.03, 21.16, 20.25, 13.52 respectively, P < 0.01); FT3 levels in C and D groups were significantly decreased as compared to A and B groups (F = 21.16, P < 0.05). rT3 level in D group was significantly decreased compared with A,B and C groups (F = 13.52, P < 0.05). At the end of six months, the levels of serum TH in E group (TT4 (51.84 +/- 15.83) nmol/L, TT3 (0.77 +/- 0.22) nmol/L, FT4 (6.88 +/- 2.23) pmol/L, FT3 (0.74 +/- 0.28) pmol/L, rT3 (0.14 +/- 0.03) nmol/L) were lower than those in any other groups (F values were 6.05, 12.22, 11.25, 13.42, 5.89 respectively, P < 0.05). At the end of both three and six months, the mRNA levels of CCK gene in E group were lower than any other groups (F values were 4.04, 3.95 respectively, P < 0.01). The results of correlation analysis showed that serum FT4 had linear correlation with levels of CCK mRNA (r values were 0.990, 0.948 respectively; P < 0.05); However serum FT3 had no linear correlation with the levels of CCK mRNA (r values are 0.970, 0.932 respectively).
  
  
  CONCLUSIONS
  Exposure to overdose of iodine (iodine ration was 100-fold higher than that of A group) could decrease the mRNA level of CCK gene. Compared with FT3, FT4 might have more important role on the regulation of CCK mRNA induced by excess of iodine.
authors.affiliation: Metabolic Disease Hospital and Endocrinology Institute of Tianjin Medical University, Key Laboratory of Hormones and Development of Ministry of Health, Tianjin 300070, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Zheng
authors.forename: Gang
authors.initials: G
authors.lastname: Guo
authors.forename: Bao-Li
authors.initials: BL
authors.lastname: Wang
authors.forename: Dong-Chun
authors.initials: DC
authors.lastname: Liang
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.forename: Jing-Yu
authors.initials: JY
authors.lastname: Zhang
authors.forename: Xue-Qin
authors.initials: XQ
authors.lastname: Zhao
authors.forename: Zu-Pei
authors.initials: ZP
authors.lastname: Chen
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002766:Cholecystokinin / Q000096:biosynthesis* / Q000235:genetics; D062787:Drug Overdose; D005260:Female; D005526:Food, Formulated; D015870:Gene Expression; D006963:Hyperphagia; D007455:Iodine / Q000633:toxicity*; D008297:Male; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D013963:Thyroid Hormones / Q000097:blood*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D012333:RNA, Messenger; D013963:Thyroid Hormones; D014284:Triiodothyronine; D013972:Thyrotropin; D002766:Cholecystokinin; D007455:Iodine; D013974:Thyroxine