Journal of Applied Physiology, Vol 80, Issue 3 971-980, Copyright © 1996 by American Physiological Society
Experimental modification of rat pituitary prolactin cell function during and after spaceflight
W. C. Hymer, T. Salada, L. Avery and R. E. Grindeland
Department of Biochemistry and Molecular Biology, Pennsylvania State University 16802, USA.
This study was done to evaluate the effects of microgravity on prolactin
(PRL) cells of the male rat pituitary gland. We used the identical passive
closed-vial cell culture system that was described for the culture of
growth hormone cells (W. C. Hymen, R. E. Grindeland, T. Salada, P. Nye, E.
Grossman, and P. Lane. J. Appl. Physiol. 80:955-970, 1996). After an 8-day
spaceflight, all flight media (containing released PRL), as well as
extracts (containing intracellular PRL), contained significantly lower
amounts of immunoreactive PRL than their corresponding ground control
samples. On the other hand, these same samples, when assessed for their
biological activities by two different in vitro lymphocyte assays, yielded
disparate results that may reflect posttranslational modifications to the
hormone molecule. Other data showed that 1) the apparent molecular weights
of released PRL molecules were not altered by microgravity, but 2) the
region from which the PRL cells came (dorsal or ventral) made a significant
difference in the amount and activity of PRL released from the flight
cells. Because there is much current interest in the role that PRL may play
in the regulation of the immune system and because changes in both cellular
and humoral immunity accompany spaceflight, this study could help define
future microgravity research in this area.
