Rat anterior pituitary hormone cells: responses to variable gravity.
BACKGROUND
While life science data dealing with effects of hypogravity are accumulating, relatively little is known about the effects of hypergravity at the level of either the whole animal or the individual cell. The purpose of this experiment was to compare data collected on cells of anterior pituitaries from animals centrifuged at 2G using an experimental design that was identical to that of a spaceflight experiment performed in 1989.


OBJECTIVE
Centrifugation of the animal at 2G for 14 d alters the function and morphology of cells of the anterior pituitary in subsequent in vitro tests at 1G.


METHODS
Intact rats were centrifuged at twice Earth's gravity for 14 d in a specially designed animal centrifuge as part of the Cosmos 2G study. This study was designed to replicate a previous spaceflight experiment so that direct comparisons between hyper- (centrifugation, 2G) and hypogravity (spaceflight, 0.001G) could be made. Anterior pituitary cells were then evaluated for cell function and morphology in a variety of post-flight tests.


RESULTS
Growth hormone cells from centrifuged animals released less bioactive, but not immunoreactive, growth hormone (GH) than cells from non-centrifuged animals. This was also true for GH released in response to provocative stimulation by a synthetic peptide (growth hormone releasing hormone, GHRH) that causes GH release after binding to cell membrane receptors. Cell morphology was also different between cells from centrifuged and control animals; cells in the experimental group were smaller and less granulated. However, another type of hormone-producing cell contained in these preparations, viz. prolactin cells, was not affected by centrifugation.


CONCLUSIONS
Centrifugation of animals for 14 d alters both the in vitro release of GH and GH cell morphology relative to corresponding controls from non-centrifuged animals. Because prolactin cells are not affected by centrifugation, the response is specific to the GH cell.
Shellenberger
K E
KE
Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, USA.
Grindeland
R E
RE
Hymer
W C
WC
D000818:Animals; D001681:Biological Assay; D048429:Cell Size; D002498:Centrifugation / Q000009:adverse effects*; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D013006:Growth Hormone / Q000502:physiology; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology; D018471:Hypergravity / Q000009:adverse effects*; D018472:Hypogravity / Q000009:adverse effects*; D007150:Immunohistochemistry; D010903:Pituitary Gland, Anterior / Q000166:cytology* / Q000502:physiology*; D011388:Prolactin / Q000502:physiology; D051381:Rats; D013026:Space Flight; D013997:Time Factors
D011388:Prolactin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone