| Project/Area Number |
03660278
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
畜産学(含草地学)
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| Research Institution | Shizuoka University |
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Principal Investigator |
MIZUNO Hideo Shizuoka University, Faculty of Agriculture, Professor, 農学部, 教授 (30022164)
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| Co-Investigator(Kenkyū-buntansha) |
SENSUI Naoto Nihon University, Coll. of Agric. Vet. Sci., Assoc. Prof., 農獣医学部, 講師 (10060120)
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| Project Period (FY) |
1991 – 1992
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| Project Status |
Completed (Fiscal Year 1992)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1992: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1991: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | Mammary function / Lactation number / Aging / Mammary cell proliferation / 連産 / プロラクチン / 乳腺分他増殖 / ホルモン / 単層培養 |
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| Research Abstract |
It is well known that the amount of milk produced by cows changes with advancing age and increased number of lactations. Some explanation has been given for this but no experimental evidence has been provided. Therefore, the present study was conducted to elucidate the mechanism by which mammary function changes with recurring pregnancy and aging. Four lactations were successively established in mice. Mammary secretory function was lower in the 1st than in the 2nd and 3rd lactations despite that no difference existed in mammary cell numbers. In the 4th lactation, milk yield reduces with decreased number of mammary cells and reduced food intake. Differences in mammary growth response to a given dose of estrogen and progesterone between mice at different ages and between parous and nuliparous mice at the same age were shown. Also, cultured dispersed mammary epithelial cells taken from mice under these physiological conditions proliferated differently in culture media with or without chorela toxin and/or epidermal growth factor. Pituitary and serum prolactin levels changed differently between different ages and between parous and nuliparous mice in response to estrogen. Heterogeneity in pituitary prolaction was observed in old but not young rats and was induced by estrogen administration both in young and old rats. These results may provide some clue to enlighten the mechanism of change in mammary function with aging and advancing lactations.
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