title: Mice without a functional relaxin gene are unable to deliver milk to their pups.
abstract: We have used gene targeting to generate relaxin (rlx)-deficient mice. The majority (15 of 17) of homozygous (rlx-/-) mice are fertile and produce normal litters. However their mammary development is deficient; pups are unable to suckle and die within 24 h of birth unless cross-fostered to a wild-type (rlx+/+) foster mother. The nipples of rlx-/- animals do not enlarge significantly during pregnancy, and their histology retains the appearance of the virgin state. Breast parenchyma is somewhat underdeveloped at term even though milk is produced. Mammary ducts become grossly dilated in these animals. Heterozygous (rlx+/-) mice lactate normally. The interpubic ligament does not relax during pregnancy in rlx-/- mice. Plasma osmolality during late gestation was significantly higher (P < 0.001) in rlx-/- mice than in wild-type controls.
authors.affiliation: Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: L
authors.initials: L
authors.lastname: Zhao
authors.forename: P J
authors.initials: PJ
authors.lastname: Roche
authors.forename: J M
authors.initials: JM
authors.lastname: Gunnersen
authors.forename: V E
authors.initials: VE
authors.lastname: Hammond
authors.forename: G W
authors.initials: GW
authors.lastname: Tregear
authors.forename: E M
authors.initials: EM
authors.lastname: Wintour
authors.forename: F
authors.initials: F
authors.lastname: Beck
mesh_terms: D000483:Alleles; D000818:Animals; D015152:Blotting, Northern; D002874:Chromosome Mapping; D005260:Female; D018390:Gene Targeting; D007774:Lactation / Q000235:genetics*; D008321:Mammary Glands, Animal / Q000166:cytology / Q000196:embryology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation; D009994:Osmolar Concentration; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011631:Pubic Symphysis / Q000196:embryology; D012065:Relaxin / Q000235:genetics* / Q000502:physiology; D013234:Stem Cells / Q000737:chemistry / Q000378:metabolism*
chemical_list: D012065:Relaxin