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Effects of Spaceflight on Anterior Pituitary Receptors (SLS1 BSP21)
Principal Investigator
Research Area:
Species Studied
Scientific Name: Rattus norvegicus Species: Rat Strain: Sprague-Dawley


It has been found that the secretion of growth hormone (GH) is decreased during exposure to actual or simulated microgravity. GH is secreted by somatotrophs in the anterior pituitary and is the primary regulator of growth. The release of GH is under the control of two hypothalmic peptides, stimulatory growth hormone releasing factor (GRF) and the inhibitor somatostatin (SS). GRF acts on the specific cell receptors of somatotrophs thus activating the release of GH. Increased numbers of GH content and GH granules in somatotrophs after spaceflight suggests that the decrease in GH secretion not due to a decrease in synthesis of GH but rather a decrease in secretion. The hypothesis of this experiment is that spaceflight causes an alteration in the number and/or affinity of GRF receptors that accounts for the decrease in GH secretion.

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Somatotropin-releasing hormone
Pituitary hormones

Data Information
Data Availability
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Activity, motor, Rat, Microgravity, SLS-1 (counts)
Response, Binding affinity, growth hormone releasing factor (GRF), pituitary, rat, Competitive binding radioassay
Response, Binding capacity, growth hormone releasing factor (GRF), pituitary, rat, Competitive binding radioassay
Weight, tissue (organ), Pituitary, rat, Balance (CGS units)
Weight, tissue (organ), Various, rat, Balance (CGS units)
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Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
STS-40 06/05/1991 06/14/1991 9 days

Additional Information
Managing NASA Center
Ames Research Center (ARC)
Responsible NASA Representative
Ames Research Center LSDA Level 3
Project Manager: Martha Del Alto
Institutional Support
National Aeronautics and Space Administration (NASA)
Protocol / Approach
Synchronous control
51Cr-red cells
Vivarium control