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Neither Milk Production, Milk Transfer Nor Pup Growth Hormone Account for Reduced Body Weights of Rat Pups Reared In HypergravityStudies spanning the gravity continuum from 0 to 2-g are revealing new insights into how mammalian reproduction and development may proceed in the microgravity of space. Rat pups reared from either conception or midgestation in hypergravity (hg) weigh 6-15% less than 1-g controls. In the present study we analyzed maternal and pup factors that may account for reduced body weight of hg reared pups. Beginning on Gestational day (G)11 of the rats' 22 day pregnancy, rat dams and their litters were continuously exposed to either 1.5-g, 1.75-g or 2.0-g. Prolaction (Prl) and oxytocin (OT) were measured in hg-exposed dams during either pregnancy (G20) or lactation (Postnatal day [P] 10). Gravity related differences in Prl were not observed whereas OT was depressed during lactation in hg dams relative to controls (p less than 0.05). Milk transfer measured during a discrete suckling episode was actually increased in hg-reared litters and comparable numbers of milk-letdowns were observed in the two conditions. Recent reports using dwarfing phenotypes in mouse mutants have provided evidence for postnatal dependence on growth hormone (GH) and insulin-like growth factors (IGFs). Plasma GH measured in P10 pups using enzyme immunoassay (EIA) was significantly elevated in hg pups relative to 1-g controls (mean +/- sd., ng/ml: 2.0-g, 10.6 [3.0], 1.5-g 8.9 [4.0], 1.0-g, 7.95 [3.1]). Together, these findings suggest that neither milk production, milk transfer nor pup GH play significant roles in reduced body weights of hg-reared pups. Studies underway are focused on insulin-like growth factors.
Document ID
20020079885
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Bear, L. A.
(NASA Ames Research Center Moffett Field, CA United States)
Chowdhury, J. H.
(Alberta Univ. Canada)
Grindeland, R. E.
(NASA Ames Research Center Moffett Field, CA United States)
Wade, C. E.
(NASA Ames Research Center Moffett Field, CA United States)
Ronca, A. E.
(NASA Ames Research Center Moffett Field, CA United States)
Dalton, Bonnie
Date Acquired
August 20, 2013
Publication Date
January 1, 2002
Subject Category
Life Sciences (General)
Funding Number(s)
PROJECT: RTOP 121-10-30
CONTRACT_GRANT: NIMH-MH46485
PROJECT: RTOP 121-10-50
PROJECT: RTOP 121-40-10
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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