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Effects of Hypergravity Rearing on Growth Hormone (GH) Secretion In Preweanling RatsWe previously reported that rat pups reared at 1.5-g, 1.75 or 2.0-g hypergravity weigh 6-15% less than 1.0-g controls. To account for these findings. we measured the lactational hormones, prolaction (Prl) and oxytocin (OT), in the pups' mothers. Gravity related differences in Prl were not observed whereas OT of lactating dams was significantly reduced relative to controls. Milk transfer from dam to pup was not impaired in hypergravity-reared litters tested at 1-g. Together, these findings suggest that impaired lactation and milk transfer do not account for reduced body masses of postnatal rats reared in hypergravity. In the present study, we analyzed growth hormone (GH) secretion and maternal licking in pups reared in hypergravity and in 1.0-g controls. Recent reports using dwarfing phenotypes in mouse mutants have provided evidence for postnatal dependence on GH and insulin-like growth factors (IGFs). Beginning on Gestational day (G)11 of the rats' 22 day pregnancy, rat dams and their litters were exposed to either 1.5-g, 1.75-g or 2.0-g. On Postnatal day (P)10, we measured plasma GH using enzyme immunoassay (EIA). Contrary to our hypothesis, GH was significantly elevated in pups reared at 2.0-g relative to 1.0-g controls. Pup-oriented behaviors of the hypergravity dams were also changed, possibly accounting for the increase in pup GH. GH alone does not appear to play a role in reduced body weights of hypergravity-reared pups.
Document ID
20020079819
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Baer, L. A.
(Lockheed Martin Corp. Moffett Field, CA United States)
Chowdhury, J. H.
(Alberta Univ. Canada)
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 121-10-50
CONTRACT_GRANT: NIMH-MH46485
PROJECT: RTOP 121-10-30
PROJECT: RTOP 121-40-10
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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