Effects of hypergravity on ovarian-hypophyseal function in antepartum and postpartum rats.
BACKGROUND
Rats exposed to microgravity during the post-implantation phase of pregnancy had minimal alterations in ovarian and hypophyseal parameters during the antepartum and postpartum periods. In the current study, a similar parallel experimental design was employed to ascertain the effects of hypergravity on ovarian and hypophyseal function.


OBJECTIVE
We hypothesized that hypergravity exposure during the post-implantation stage of pregnancy would not alter antepartum and postpartum ovarian and hypophyseal function.


METHODS
Pregnant rats were assigned to hypergravity (1.5 G, 1.75 G, or 2.0 G), rotational control, or stationary control groups (n = 10 each group) beginning on gestation day 11 and ending on day 20. Hypophyseal and ovarian analyses were conducted on 5 of the animals from each group at day 20. The remaining animals in each group were allowed to go to term and the same analyses were conducted 3 h postpartum.


RESULTS
Hypergravity at all levels decreased the percent body mass gain from gestation day 11 to 20 (p < 0.05); however, the wet weight of the pituitaries and ovaries was not changed. There was no effect of hypergravity on the number of healthy or atretic antral follicles of any size at gestation day 20 or postpartum. The number of corpora lutea of pregnancy was decreased in all hypergravity groups, but the number of live fetuses at gestation day 20 or pups at term was not altered. Plasma concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin, and progesterone were not changed at gestation day 20 or postpartum. Pituitary content of LH, FSH, and prolactin was not altered by hypergravity at gestation day 20, but LH content was significantly increased (p < 0.05) at 1.5 and 1.75 G postpartum.


CONCLUSIONS
We conclude that hypergravity, up to and including 2.0 G, is compatible with maintenance of pregnancy and has minimal effects on hypophyseal parameters. Ovarian follicles are not altered by hypergravity, but corpora lutea may regress at a more rapid rate.
Burden
Hubert W
HW
Department of Anatomy and Cell Biology, Brody School of Medicine, East Carolina University, Greenville, NC 27858, USA. burdenh@mail.ecu.edu
Zary
Joan T
JT
Hodson
Charles A
CA
Gregory
Heather L
HL
Baer
Lisa A
LA
Ronca
April E
AE
D000818:Animals; D015992:Body Mass Index; D005260:Female; D018471:Hypergravity / Q000009:adverse effects*; D006080:Ovarian Follicle / Q000502:physiology; D010053:Ovary / Q000033:anatomy & histology / Q000502:physiology*; D010902:Pituitary Gland / Q000502:physiology*; D049590:Postpartum Period; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley