To observe the changes of sodium iodide symporter (NIS) in mammary gland of rats at different lactation periods, and to explore iodine uptake mechanism.

Seventy-five adult Wistar rats were selected, including 60 females, 15 males, weighting 220-250 g. All female Wistar rats were divided into 4 groups according to their body mass via random number table method: normal non-pregnant group, lactating for 7-, 14- and 21- day groups, 15 rats in each group. All rats were fed with adequate conventional fodder and tap water. In addition to normal non-pregnant group, other three groups of female and male rats were mated at 3∶1, respectively, then after lactating for 7th, 14th and 21th days, mammary gland tissues were harvested. The expressions of NIS mRNA and protein were measured with real time quantitative PCR (qRT-PCR) and immunohistochemical staining, respectively.

NIS protein was expressed in the small ductal epithelium of mammary gland and the basal lateral membrane under light microscope, obvious brown particles visible. The expression of NIS mRNA (0.79 ± 0.11, 1.05 ± 0.21, 0.98 ± 0.18, 0.89 ± 0.16) in mammary gland showed significant differences between groups (F=5.965, P < 0.05), the expressions of NIS mRNA in 7th and 14th day groups were higher than that of normal non-pregnant group (P < 0.05). The expression of NIS protein in mammary gland showed significant differences between groups (H=32.747, P < 0.05), the staining intensity of mammary gland tissue after lactating for 7th, 14th and 21th days groups was stronger than that of normal non-pregnant rats (P < 0.05).

NIS is expressed in mammary gland of rats at different lactation periods. The iodine uptake of mammary gland is enhanced in early lactation period.

Lactation; Rats; Mammary gland; Sodium iodide symporter