ASGSB 1999 Annual Meeting Abstracts


MICROGRAVITY INDUCES APOPTOSIS IN LUTEAL CELLS OF THE PREGNANT RAT. H. Yang, G. K. Bhat, and R. Sridaran. Department of Physiology, Morehouse School of Medicine, Atlanta, GA.

We have demonstrated that microgravity suppresses steroidogenesis by luteal cells in the pregnant rat. A few recent studies have shown that microgravity also induces changes at the cellular level including alteration in the cytoskeletal organization and apoptosis. However, it is not well understood whether microgravity induces apoptosis in luteal cells. Therefore, the purpose of this study was to assess whether apoptosis plays any role in suppressing steroidogenesis by luteal cells cultured under microgravity conditions. The luteal cells were isolated from the corpora lutea of day 8 pregnant rats and placed in equal numbers in slide flasks. One slide flask was placed in a clinostat and the other was a stationary control. At 48 hours, progesterone levels were suppressed by microgravity (1.61 vs 2.70 ng/ml in control); apoptosis of cultured luteal cells was examined by TUNEL and comet assays. The number of apoptotic cells was higher in the clinostat as seen by TUNEL (24.55 vs 10.71 % in control). Comet-tails, which are characteristic of apoptosis, increased in luteal cells of the clinostat when compared to that of the stationary control. These apoptotic cells were clearly distinguished from necrotic cells after staining with Hoechst and propidium iodide. Many cells were stained with Hoechst, whereas cells stained with propidium iodide were rare in both indicating that most of the cells cultured in the clinostat are undergoing apoptosis, but not necrosis. These results suggest that microgravity induces apoptosis in cultured luteal cells. To further confirm the induction of luteal cell apoptosis by microgravity, 3-end DNA labeling is being performed to detect the DNA laddering. (Supported by a grant from NASA: NAG9-963 to RS).


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