1997 Fiscal Year Final Research Report Summary
Effective Expression of Prolactin Receptor Gene and its Relationship with Milk Production
| Project/Area Number |
08456139
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied animal science
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| Research Institution | The University of Tokyo |
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Principal Investigator |
SAKAI Senkiti Univ.of Tokyo, Grad.Sch.of Agri.and Life Sci., Professor, 大学院・農学生命科学研究所, 教授 (80114487)
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| Co-Investigator(Kenkyū-buntansha) |
KOHMOTO Kaoru Nippon Veterinary and Animal Scinece College, Visiting Professor, 獣医畜産学部, 客員教授 (30011894)
HAYASHI Yoshihiro Univ.of Tokyo, Grad.Sch.of Agri.and Life Sci., Professor, 大学院・農学生命科学研究所, 教授 (90092303)
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| Project Period (FY) |
1996 – 1997
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| Keywords | PROLACTIN RECEPTOR / PROLACTIN RECEPTOR GENE / LACTOGENESIS / MAINTENANCE OF LACTATION / MAMMARY GLAND |
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| Research Abstract |
1. Prolactin receptor gene expression at lactogenesis
In the mouse mammary gland, the level of prolactin receptor mRNA decreased about 60% during the first 5 days of pregnancy, and its low levels were maintained until 10 : 00 on day 18 of pregnancy. The level of prolactin receptor mRNA increased about 6 folds during the next 12 h period. The high level was maintained on day zero of lactation. The increase in the prolactin receptor mRNA was caused by the increase in corticosterone in vivo and in vitro. The similar changes were found in the ovariectomized midpregnant mouse mammary gland. It is concluded that the prolactin receptor gene expresses about 12 h before the onset of parturition.
2. Effect of accumulation/removal of milk on prolactin receptor gene expression
Prolactin receptor mRNA in the lactating mouse mammary gland began to decrease 12 h after removal of pups from their mother and its level was the lowest at 18 h. Mice which had been weaned for 24 h were allowed to nurse foster pups for 6 h. Prolactin receptor mRNA was restored during the 6 h-nursing period. The number of prolactin receptor changed in parallel with the level of prolactin receptor mRNA.Prolactin receptor gene expression slowed when the mammary gland accumulated milk maximum. Prolactin receptor mRNA increased in the mammry gland in which milk was suckled by the pups. It is concluded that the main factor controlling the prolactin receptor gene expression is the degree of milk accumulation in the mammary gland.
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