Journal of Applied Physiology, Vol 73, Issue 2 166S-168S, Copyright © 1992 by American Physiological Society
Pituitary oxytocin and vasopressin content of rats flown on COSMOS 2044
L. Keil, J. Evans, R. Grindeland and I. Krasnov
National Aeronautics and Space Administration Ames Research Center, Moffett Field, California 94035.
Preliminary studies in rats (COSMOS 1887) suggested that levels of
posterior pituitary hormones were reduced by exposure to spaceflight. To
confirm these preliminary findings, we obtained pituitary tissue from rats
flown for 14 days on COSMOS 2044. Posterior pituitary content of oxytocin
(OT) and vasopressin (VP) were measured in these tissues as well as those
from ground-based controls. The synchronous control group had feeding and
lighting schedules synchronized to those in the spacecraft and were
maintained in flight-type cages. Another group was housed in vivarium
cages; a third group was tail suspended (T), a method used to stimulate
microgravity. Flight rats showed an average reduction of 27% (P less than
0.05) in pituitary OT and VP compared with the three control groups. When
hormone content was expressed in terms of pituitary protein (micrograms
hormone/mg protein), the average decrease in OT and VP for the flight
animals ranged from 20 to 33% (P less than 0.05) compared with the various
control groups. Reduced levels of pituitary OT and VP were similar to
preliminary measurements from the COSMOS 1887 mission and appear to result
from exposure to spaceflight. These data suggest that changes in the rate
of hormone secretion or synthesis may have occurred during exposure to
microgravity.
