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Objective To observe the variation of phosphatidylinositol-3 kinase (PI3K),protein kinase B (AKT),sodium iodide symporter (NIS) mRNA and protein expression in rat mammary tissues and serum insulin growth factor Ⅰ (IGF-1) under different iodine nutrition levels,and to study the role of PI3K-AKT signaling pathway in the process of mammary gland intaking iodine during lactation period.Methods Totally 130 Wistar rats (100 female rats,30 male rats) were randomly divided into five groups with 20 female rats in each group:①control group (NI):was feed with normal diet and iodine content 50 μg/L in deionized water;②low iodine group 1 (LI1 group):was feed with low iodine diet and deionized water;③low iodine group 2 (LI2):was feed with low iodine diet and iodine content 5 μg/L in deionized water;④high iodine group 1 (HI1 group):was feed with normal diet and iodine content 3 000 μg/L in deionized water;⑤high iodine group 2 (HI2):was feed with normal diet and iodine content 10 000 μg/L in deionized water.After feeding for 3 months,females were mated with male rats,then male rats were taken out and every female rat was feed individually.Urinary iodine level of rats in lactation period 10 days after giving birth was tested.Blood and mammary tissue samples of rats in lactation period were taken after killing them.Enzyme linked immunosorbent assay (ELISA) was used to detect serum IGF-1 level,real-time fluorescence quantification PCR to detect the mRNA expression of mammary gland PI3K,AKT and NIS,Western blotting to detect mammary gland PI3K,total AKT,phosphorylation AKT (p-AKT) and NIS protein expression.Results The medians urinary iodine of lactation period rats in LI1 and LI2 (3.16,6.36 μg/L) were significantly lower than that in NI group (162.59 μg/L),and were significantly higher in HI1 and HI2 (2 356.27,11 507.29 μg/L) than that in NI group.The differences were statistically significant (all P ＜ 0.01).Compared with control group [(8.84 ± 2.12) μg/L],the content of serum IGF-1 increased significantly in lactation period rats in LI1 and LI2 groups [(13.30 ± 2.37) and (10.90 ± 1.92) μg/L,all P＜ 0.01].The real-time fluorescence quantification PCR detection results indicated that the differences were statistically significant by comparing NIS,AKT,PI3K mRNA expression of the mammary tissues of lactation period rats in the five groups (F=14.916,36.477,14.994,all P＜ 0.01).Among them,NIS mRNA expression quantities in LI1 and LI2 groups (0.75 ± 0.40,0.89 ± 0.51) were significantly higher than that in NI group (0.53 ± 0.31),and significantly lower in HI2 group (0.30 ± 0.24) than that in NI group (P ＜ 0.05 or ＜ 0.01).AKT mRNA expression quantities in LI1 and LI2 groups (0.90 ± 0.19,0.64 ± 0.22) were significantly higher than that in NI group (0.43 ± 0.22),and significantly lower in HI2 group (0.29 ± 0.15) than that in NI group (P ＜ 0.05 or ＜ 0.01).PI3K mRNA expression quantity in LI1 group (0.85 ± 0.42) was significantly higher than that in NI group (0.50 ± 0.24),and significantly lower in HI2 group (0.28 ± 0.10) than that in NI group (all P ＜ 0.01).Western blot detection results indicated that the differences were statistically significant by comparing mammary gland NIS protein expression of lactation period rats in the five groups (F=4.510,P＜ 0.01).Among them,LI1 group (1.67 ± 0.97) was significantly higher than NI group (0.87 ± 0.43,P ＜ 0.05).The differences were statistically significant by comparing the p-AKT protein expression among groups (F =3.528,P ＜ 0.05).Among them,HI2 group (1.10 ± 0.30) was significantly higher than NI group (0.75 ± 0.23,P ＜0.05).The differences were not statistically significant by comparing total AKT and PI3K protein expression among groups (F =0.558,1.319,all P ＞ 0.05).Conclusion The inhibitory effect of PI3K-AKT signaling pathways on NIS in the mammary gland was weaker than the effect of iodine intake.But the expression of functional p-AKT was gradually increased with the increment of iodine intake,which had been presented inhibit effect on NIS expression in lactating mammary gland.
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Among rodents, maternal aggression in the postpartum period represents a species-typical adaptation, but when aggressive behavior increases beyond this adaptive level, it can represent a model of excessive aggression. This study assessed the neuroendocrine response of lactating rats and socially instigated male rats. The aim of the present study was to assess neuroendocrine responses and the behavioral pattern of lactating rats and males that were subjected to an emotional stressor using the social instigation protocol. We measured plasma corticosterone levels as the key hormonal parameter of the hypothalamic-pituitary-adrenal (HPA) axis and oxytocin, prolactin, and progesterone, which are released in response to several types of stressors. Our results showed that lactating rats that were subjected to only social instigation or aggressive confrontation in the presence of their pups had lower plasma corticosterone levels, and this response was similar to oxytocin, prolactin, and progesterone levels. By contrast, male rats showed increased corticosterone levels after being subjected only to social instigation. Male rats also engaged in aggressive behavior compared with the control group. In conclusion, this study demonstrated that lactating rats subjected to social instigation exhibited an attenuation of the HPA axis response, which is considered to be crucial to the dam's welfare so that it can care for its offspring. Thus, we can infer that lactation is a relevant factor in neuroendocrine responses to stress because of the increased levels of corticosterone in males.
Assuntos
Agressão , Animais Lactentes , Comportamento Animal , Corticosterona , Comportamento SocialRESUMO
In adult female mammals, reproductive experience (e.g., mating, pregnancy, parturition, and lactation) has long-term behavioral, endocrine, and neurochemical implications. This experience causes behavioral and neurochemical changes that involve several brain areas important for the expression of maternal behavior. The present study showed that lactating rats exhibited reduced general locomotor activity in the open field test compared with virgin animals. Our hypothesis was that nucleus accumbens dopamine, which regulates maternal behavior in lactating rats, is also involved in the low expression of maternal locomotion in the open field test observed during the early stages of lactation and reflects decreased motivation. Initially we compared open field behavior in virgin and lactating rats to confirm our previous data. Thus, the in vivo release of dopamine in the nucleus accumbens in virgin and lactating female rats was measured. Perfusate concentrations of extracellular dopamine and its metabolites showed no differences between virgin and lactating rats. Thus, the reduced general activity observed in lactating rats might not be related to intra-nucleus accumbens dopamine control.