title: Early down-regulation of milk production after weaning by pup removal and prior to involution in mouse mammary glands.
abstract: The mammary gland is a highly specialized organ that is able to repeat development and regression (involution) of alveolar structures for milk production. Mammary involution consists in two phases. The first phase is reversible and lasts until approximately 48 h after weaning in mice. Interestingly, an extended milking interval can change the milk-secretory activity of alveolar epithelial cells (AECs) before the first phase of involution begins. In this study, we investigate the changes in the ability of AECs to secrete milk during the involution progression. Careful observation of the number and locations of cleaved caspase-3 positive AECs revealed that the first phase of involution occurred approximately 24 h after weaning and the second phase began between 48 and 72 h after weaning. However, initial changes in the milk production ability of AECs began just 1 h after weaning and milk production gradually ceased within 24 h. In addition, activation of STAT3 and inactivation of STAT5 had occurred in some AECs by 6 h after weaning and more broadly by 24 h. In addition, milk production processes such as nutrient uptake, synthesis, and secretion ceased by 24 h post-weaning. Interestingly, enlarged cytoplasmic lipid droplets were observed in AECs 12 h after weaning even though the expression levels of genes relevant to triglyceride production (Srebp1 and AQP3) were down-regulated. These results indicate that several changes in the milk production ability of AECs occur during expanded suckling intervals and prior to involution.
authors.affiliation: Laboratory of Dairy Food Science, Research Faculty of Agriculture, Hokkaido University, North 9, West 9, Sapporo, 060-8589, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Uejyo
authors.affiliation: Laboratory of Dairy Food Science, Research Faculty of Agriculture, Hokkaido University, North 9, West 9, Sapporo, 060-8589, Japan.
authors.forename: Chinatsu
authors.initials: C
authors.lastname: Kuki
authors.affiliation: Laboratory of Dairy Food Science, Research Faculty of Agriculture, Hokkaido University, North 9, West 9, Sapporo, 060-8589, Japan.
authors.forename: Shoko
authors.initials: S
authors.lastname: Oyama
authors.affiliation: Laboratory of Dairy Food Science, Research Faculty of Agriculture, Hokkaido University, North 9, West 9, Sapporo, 060-8589, Japan.
authors.forename: Haruto
authors.initials: H
authors.lastname: Kumura
authors.affiliation: Laboratory of Dairy Food Science, Research Faculty of Agriculture, Hokkaido University, North 9, West 9, Sapporo, 060-8589, Japan. kkobaya@anim.agr.hokudai.ac.jp.
authors.forename: Ken
authors.initials: K
authors.lastname: Kobayashi
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002364:Caseins / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D015536:Down-Regulation; D005260:Female; D005786:Gene Expression Regulation; D008321:Mammary Glands, Animal / Q000254:growth & development* / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008813:Mice, Inbred ICR; D008892:Milk / Q000378:metabolism*; D008954:Models, Biological; D000070780:Perilipin-2; D050796:STAT3 Transcription Factor / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000378:metabolism; D013997:Time Factors; D014886:Weaning
chemical_list: D002364:Caseins; D008565:Membrane Proteins; D000070780:Perilipin-2; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D053148:Caspase 3