title: Transmission of relaxin and estrogens to suckling canine pups via milk and possible association with hip joint laxity.
abstract: OBJECTIVE
  To determine whether abnormal laxity of hip joints of canine pups with genetic predisposition to hip dysplasia (HD+) is related to ingestion of milk-borne hormones.
  
  
  METHODS
  7 female Labrador Retrievers with HD+ and 8 with low predisposition to hip dysplasia (HD-) and their offspring.
  
  
  METHODS
  Immunoactive relaxin, estrogen, and estrogen precursor concentrations in milk of HD+ lactating bitches and in serum of their pups were compared with those of HD- bitches and pups. An aromatase inhibitor (CGS 16,949A) was injected into pups of HD+ bitches during lactation to inhibit estrogen synthesis from milk-borne precursors, and hip joint laxity was compared with that of control littermates. Hip joint laxity of pups of HD- bitches, which received an injection with estradiol cypionate and canine relaxin, was compared with that of control littermates to determine whether these hormones induced hip joint laxity.
  
  
  RESULTS
  High concentrations of estrogens and relaxin were found in milk of HD+ and HD- bitches throughout lactation. Serum concentrations of milk-derived relaxin and total estrogens were similar in all pups, but estradiol-17B was detected only in pups of HD+ bitches. Hip joint laxity was reduced in pups that received CGS 16,949A. Hip joint laxity was INCREASED IN PUPS OF HD- BITCHES THAT RECEIVED ESTRADIOL CYPIONATE AND RELAXIN.
  
  
  CONCLUSIONS
  Milk-borne maternal hormones and precursors were absorbed into the circulation of canine neonates and may play a role in hip joint laxity in HD+ pups. Phenotypic expression of hip dysplasia may therefore be preventable by antihormone treatment.
authors.affiliation: Nelson Institute of Environmental Medicine, School of Medicine, New York University, Tuxedo, NY 10987, USA.
authors.forename: Bernard G
authors.initials: BG
authors.lastname: Steinetz
authors.forename: Alma J
authors.initials: AJ
authors.lastname: Williams
authors.forename: George
authors.initials: G
authors.lastname: Lust
authors.forename: Christian
authors.initials: C
authors.lastname: Schwabe
authors.forename: Erika E
authors.initials: EE
authors.lastname: Büllesbach
authors.forename: Laura T
authors.initials: LT
authors.lastname: Goldsmith
mesh_terms: D000818:Animals; D000833:Animals, Suckling; D004285:Dogs; D004958:Estradiol / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism; D004965:Estrogen Antagonists / Q000627:therapeutic use; D004967:Estrogens / Q000009:adverse effects / Q000378:metabolism*; D017316:Fadrozole / Q000627:therapeutic use; D005260:Female; D020022:Genetic Predisposition to Disease; D006619:Hip Dysplasia, Canine / Q000235:genetics / Q000517:prevention & control; D006621:Hip Joint / Q000187:drug effects*; D007774:Lactation; D008022:Ligaments; D008297:Male; D008892:Milk / Q000737:chemistry; D011863:Radioimmunoassay; D012065:Relaxin / Q000009:adverse effects / Q000378:metabolism*
chemical_list: D004965:Estrogen Antagonists; D004967:Estrogens; D004958:Estradiol; C007630:estradiol 17 beta-cypionate; D012065:Relaxin; D017316:Fadrozole