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LACK OF EFFECTS OF HYPERGRAVITY ON PREGNANCY  MAINTENANCE  AND CONNEXIN 26 AND 43 IN THE PREGNANT AND POST PARTUM UTERUS OF RATS.  H.Burden¹, J. Zary¹, L. Baer², and A. Ronca². ¹Dept. of Anatomy & Cell Biology, Brody School of Med., East Carolina Univ., Greenville, NC and ²Developmental Gravitational Biology Laboratory, NASA Ames Research Center, Moffett Field, CA.

   In a previous study using pregnant rats, we showed that space flight with its associated microgravity decreased connexin 43, the major gap junction protein in the myometrium, but did not affect connexin 26, localized primarily in epithelial cells of the endometrium (Burden et al., J. Reprod. Fertil. (1999) 116: 229-234.) Since the biological effects of altered gravity may vary across the continuum from microgravity to 1-g to hypergravity, the objective of the present study was to examine the effects of hypergravity on these uterine connexins in a parallel experimental design. Pregnant rats were subjected to three levels of hypergravity (1.5, 1.75 and 2.0-g) produced by centrifugation during gestation days 11-20.  At day 20 of pregnancy, rats were removed from the centrifuge. Half the animals were euthanized for analysis and the other half was allowed to go to term and deliver. The rotational control and all hypergravity groups showed significantly less (p<0.05) weight gain during the gestation days 11-20 interval but the number of live fetuses was not different. Animals allowed to go to term had similar body mass by day 22 and delivered comparable numbers of pups on days 22 or 23. Myometrial connexin 43 was not altered by hypergravity at day 20 or three hours after delivery. Also, the degree of phosphorylation of connexin 43 was not different at day 20 or three hours after delivery in any of the treatment groups. Lastly, connexin 26, localized primarily in uterine epithelium, was similar in all groups. Thus, hypergravity, initiated after pregnancy is well established, and terminated prior to delivery, is compatible with pregnancy maintenance, and normal delivery. In addition, uterine gap junction proteins, which help mediate the delivery process, are not altered.

(Supported by NASA grant 121-1040 and NASA-Ames Cooperative Agreement No. NCC 2-1165.)

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