Study On PRL Secretion And MRNA Expression In Different Tissues Of Small-tail Han Sheep In Different Postpartum Periods

In this study,we analyzed secretion and expression of PRL in different tissues of Small-tail Han sheep after delivery,and the expression of PRL related genes in mammary gland,in order to reveal the function of PRL and lay a theoretical foundation for elucidating the relationship between PRL and reproductive performance of ewe.A total of thirty lambing Small-tail Han sheep(74.5±5.2 kg,38?42 months old)were used in this study.The birth day of thirty ewes was the start(0 day)of the study.Ten ewes were randomly selected for Blood samples collection at 8:00 in the morning on the 7,30,55 and 70 days after delivery,and the concentration of PRL in serum was measured by ELISA.Then five of the ten ewes whose blood was collected were randomly selected for slaughter.The pituitary,hypothalamus,mammary gland,ovary,uterus,lymph and kidney tissues were collected immediately after slaughtered,and the expression levels of PRL mRNA in different tissues and the expression levels of JAK2,STAT5A,CSN2 mRNA and p-STAT5A protein in mammary gland of Small-tail Han sheep in different postpartum periods were detected.Experimental results show that:?Within 70 days after delivery,the concentration of PRL in the serum of the experimental sheep ranged from(158.77±19.37)to(343.33±27.69)mIU/L,with an average of(245.16±72.38)mIU/L.The secretion of PRL from the 7 to the 70 days after delivery was significantly decreased(P<0.01),the highest concentration was(343.33±27.69)mIU/L on the 7-day,and the lowest concentration was(158.77±19.37)mIU/L on the 70-day.? On the 7 days after delivery,the expression level of PRL gene in different tissues of Small-tail Han sheep ranked from high to low was:pituitary,hypothalamus,ovary,mammary gland,uterus,lymph,kidney;on the 30 days after delivery,the expression level of PRL gene ranked from high to low was pituitary,hypothalamus,mammary gland,ovary,uterus,lymph,kidney;on the 55 days after delivery,the expression level of PRL gene ranked from high to low was:pituitary,hypothalamus,mammary gland,kidney,uterus,lymph,ovary;on the 70 days after delivery,the expression level of PRL gene ranked from high to low was:pituitary,hypothalamus,lymph,kidney,mammary gland,ovary,uterus.The expression level of PRL in pituitary and hypothalamus was significantly higher than that in kidney,uterus,ovary,lymph and mammary gland in 4 postpartum periods(P<0.01),and the expression level of PRL in pituitary was significantly higher than that in hypothalamus(P<0.01),while there are no significant difference of expression level in PRL between kidney,uterus,ovary,lymph and mammary gland was not significantly different(P>0.05).? The expression level of PRL in both pituitary and hypothalamus was the highest on the 7 days after delivery,compared with that on 30,55 and 70 days after delivery(P<0.01),followed by a decreasing trend.The expression level of PRL in the pituitary and the hypothalamus was the lowest on the 70 days after delivery,significantly lower than that on the 7,30 and 55 days after delivery(P<0.01).The expression level of PRL in the mammary gland was the highest on the 30 days after delivery,significantly higher than that on the 55 and 70 days after delivery(P<0.05),but there is no significant difference between 7 and 30 days after delivery(P>0.05).The expression level of PRL in the mammary gland was the lowest on the 70 days after delivery,significantly lower than that on the 7 and 30 days after delivery(P<0.05),and no significant difference compared with that on 55 days after delivery(P>0.05).The expression level of PRL in the ovary was the highest on 7 days after delivery,which was significantly higher than that on the 30,55 and 70 days after delivery(P<0.05).The expression level of PRL in the ovary was the lowest on 70 days after delivery,significantly lower than that on 7 and 30 days after delivery(P<0.05),and not significantly different from that on the 55 days after delivery(P>0.05).There was no significant difference of expression of PRL between uterus,lymph and kidneys during postpartum period of Small-tail Han sheep(P>0.05).?The expression level of JAK2 in the mammary gland of Small-tail Han sheep was the highest on the 7 days after delivery,but there was no difference with that on 30,55 and 70 days after delivery(P>0.05).The expression level of STAT5A in the mammary gland of Small-tail Han sheep was the highest on 7 days after delivery,which was significantly higher than that on 30,55 and 70 days after delivery(P<0.01),while the difference was not significant on 30,55 and 70 days after delivery(P>0.05).The expression level of CSN2 in the mammary gland was the highest on 7 days after delivery,significantly higher than that on 30 and 55 days after delivery(P<0.05),while the difference between 30 and 55 days was not significant(P>0.05).There was no CSN2 expression in the mammary gland on the 70 days after delivery.? The relative expression level of p-STAT5A protein in the mammary glands of Small-tail Han sheep after delivery decreased gradually,and the protein expression level on 7 and 30 days after delivery was significantly higher than that on 70 days(P<0.05),and the difference between the 7,30 and 55 days were not significant(P>0.05).In conclusion,the secretion of PRL gradually decreased in Small-tail Han sheep from the 7 days to the 70 days after delivery.The expression levels of PRL mRNA in different tissues were different.The expression levels of PRL mRNA in different tissues were higher in the early stage of lactation and decreased gradually later.In mammary gland,the mRNA expression levels of JAK2,STAT5A and CSN2 were the highest in the early stage of lactation,and decreased significantly later.