Expression of thyroid-stimulating hormone receptor in mammary gland tissue of lactating rats

Abstract

Objective To observe the protein and mRNA expression of thyroid-stimulating hormone receptor (TSHR) in mammary gland tissue of lactating rats,and to explore iodine uptake mechanism.Methods Eighty adult Wistar rats (60 female and 20 male),weighting 210-250 g were selected.All female Wistar rats were randomly divided into 6 groups according to their body mass:normal non-pregnant group,lactating for 5-,10-,15-and 20-day groups and weaning for 5 days group,10 rats in each group.All rats were fed with conventional fodder and tap water freely.In addition to the normal non-pregnant group,other five groups of female and male rats were mated at 3 ∶ 1,respectively.Then the rats in all groups were killed on the 5th,10th,15th and 20th day after lactation and on the 5th day after weaning to get the mammary gland tissue.The protein and mRNA expression of TSHR were determined by immunohistochemical staining and real-time quantitative PCR.Results TSHR protein was expressed in mammary acinar and ductal epithelial cytoplasm.The expression of TSHR in mammary gland showed significant differences between groups (x2 =14.612,P ＜ 0.05),the staining intensity of mammary gland tissue in normal non-pregnant rats(weak,n =4; moderate,n =6) was weaker than that of lactating for 5 days(weak,n =2; moderate,n =3; strong,n =5) and 10 days groups(barely detectable,n =1;moderate,n =4; strong,n =5; x2 =4.113,5.250,all P＜ 0.05).The expression of TSHR mRNA in mammary gland showed significant differences between groups(F=20.488,P ＜ 0.05); the expression of TSHR mRNA in lactating for 10 days group(0.31 ± 0.06) was higher than that of lactating for 5 days group(0.22 ± 0.04,P ＜ 0.01),and the expression of lactating for 15 days group (0.16 ± 0.08) was significantly lower than that of lactating for 5 days group (P ＜ 0.05).Conclusions TSHR is widely expressed in mammary gland of lactating rats.The iodine uptake of mammary gland is enhanced in early lactation period when the body may be more susceptible to iodine deficiency,therefore iodine should be supplemented reasonably. Key words: Thyroid-stimulating hormone receptor; Mammary gland; Rats; Lactation