AJP - Regulatory, Integrative and Comparative Physiology, Vol 252, Issue 2 233-R239, Copyright © 1987 by American Physiological Society
Salivary gland ultrastructure and cyclic AMP-dependent reactions in Spacelab 3 rats
M. I. Mednieks and A. R. Hand
Environmental stimuli influencing catecholamine levels induce changes in
cyclic AMP-dependent reactions and cell morphology in the rat parotid.
Responses of salivary glands to spaceflight were determined by measurement
of cyclic AMP-mediated reactions in fresh-frozen salivary glands and by
microscopic evaluation of ultrastructure in fixed parotid glands. Decreased
cell-free protein phosphorylation occurred in parotid glands in three of
five flight animals. Protein kinase activity ratios were decreased in the
soluble and increased in the particulate fractions of Spacelab 3 (SL-3) rat
sublingual glands, compared with ground controls. Biochemical analyses show
that effects of space flight on salivary glands are similar to those
induced experimentally by physiological manipulation or alteration of
catecholamine levels. Morphological evaluation of three SL-3 rat parotid
glands showed increased numbers of lysosomes, autophagic vacuoles
containing degenerating secretory product, and accumulation of lipid
droplets. Since these animals lost weight, consistent with disruption of
food and water consumption, morphological changes may in part be due to
decreased masticatory stimulation, as occurs with reduced food intake or a
liquid diet. The observed changes may reflect physiological responses of
the gastrointestinal and autonomic systems to effects of spaceflight.
