Responses of Plasma Proenkephalin Peptide F in Rats Following 14 Days of Spaceflight

William J. Kraemer, Andrea Marie Mastro, Scott E. Gordon, L. Perry Koziris, Jill A. Bush, Jeff S. Volek, Robert S. Staron, Duncan N. French, Matthew J. Sharman, Bonzena Jemiolo, Michael R. Deschenes, Wesley C. Hymer

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Introduction. Proenkephalin peptide F [107-140] is related to the enhancement of immune function, while microgravity has been shown to cause immuno-suppression. We investigated the physiological response of proenkephalin peptide F to microgravity. Methods: There were 12 Fischer 344 female rats, ovariectomized at 10.5 wk of age, used to determine plasma concentrations of peptide F in response to a 14-d flight aboard the Columbia Space Shuttle mission STS-62. There were 36 other such rats that served as ground-based controls to separate the effects of microgravity from those of thermal stress, flight stress, and crowded habitats. Control groups of 12 rats each were kept under the following conditions: 1) 22°C vivarium, 2) 28°C vivarium, and 3) variable (Var) to mimic flight. The flight and control groups were housed in animal enclosure modules 21 d prior to flight and for the duration of the study. The rats were sacrificed within 4-5 h after landing, at which time blood samples were obtained. Results: Body weights were obtained prior to sacrifice; mean values were flight, 199 g; 22°C, 193 g; 28°C, 192 g; and Var, 194 g. The flight group produced a significantly greater (p ≤ 0.05) level of plasma peptide F (0.056 pmol · ml -1) compared with the controls (0.016, 0.022, and 0.016 pmol · ml -1 for 22°C, 28°C, and Var, respectively). Flight animals demonstrated higher corticosterone concentrations and reduced T and B cell splenocyte counts than controls. Conclusions: These data indicate that the increases in proenkephalin peptide F observed with exposure to microgravity may present an adrenal-medullary response to cope with the decreased immune function and increased stress experienced during spaceflight and landing.

Original languageEnglish (US)
Pages (from-to)114-117
Number of pages4
JournalAviation Space and Environmental Medicine
Issue number2
StatePublished - Feb 1 2004

All Science Journal Classification (ASJC) codes

  • Public Health, Environmental and Occupational Health


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