Suckling-induced prolactin release potentiates mifepristone-induced lactogenesis in pregnant rats
Suckling, starting at 19:00 h on Day 18 of pregnancy, induced a significant increase in serum prolactin concentration at 20:00 h on Day 19 of pregnancy, but no increase in mammary gland casein or lactose content. Mifepristone (2 mg/kg) injection at 08:00 h on Day 19 of pregnancy induced significant...
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Published in | Journal of reproduction & fertility Vol. 87; no. 1; pp. 147 - 153 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
England
Society for Reproduction and Fertility
01.09.1989
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Subjects | |
Online Access | Get full text |
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Summary: | Suckling, starting at 19:00 h on Day 18 of pregnancy, induced a significant increase in serum prolactin concentration at
20:00 h on Day 19 of pregnancy, but no increase in mammary gland casein or lactose content. Mifepristone (2 mg/kg) injection
at 08:00 h on Day 19 of pregnancy induced significant increases in casein, but not in lactose, 24 h after administration.
Mifepristone alone did not induce prolactin secretion, indicating that lactogenesis was induced by placental lactogen in the
absence of progesterone action. When mifepristone was injected into suckling rats, serum prolactin concentrations were higher
than in the untreated suckling rats. Casein in these rats increased significantly 12 h after mifepristone administration and
lactose at 24 h after. If the suckling mifepristone-treated rats were given two injections of bromocriptine 1·5 mg/kg) at
12:00 h on Days 18 and 19 of pregnancy, serum prolactin concentrations were not increased by suckling, but casein and lactose
concentrations in the mammary gland showed values similar to those obtained in the mifepristonetreated non-suckling rats.
Mifepristone can therefore potentiate suckling-induced prolactin release in pregnant rats, demonstrating a direct central
inhibitory action of progesterone on prolactin secretion. This suckling-induced prolactin secretion, unable to induce casein
or lactose synthesis in the presence of progesterone, enhanced significantly synthesis of these milk components in the absence
of progesterone action (rats treated with mifepristone). Fatty acid synthase, which is stimulated by the suckling stimulus
in lactating rats, was not modified by mifepristone or suckling in pregnant rats.
Keywords: prolactin; suckling; mifepristone; mammary gland; lactogenesis; progesterone |
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ISSN: | 0022-4251 1470-1626 1741-7899 |
DOI: | 10.1530/jrf.0.0870147 |