ASGSB 1999 Annual Meeting Abstracts

MICROGRAVITY SUPPRESSES PROGESTERONE PRODUCTION BY LUTEAL CELLS OF THE PREGNANT RAT. G. K. Bhat, H. Yang, and R. Sridaran. Department of Physiology, Morehouse School of Medicine, Atlanta, GA.

The purpose of this study was to assess the gravity induced changes on the production of progesterone (P) by luteal cells of the pregnant rat using an in vitro model system. Mixed population of luteal cells was isolated from the corpora lutea of day 8 pregnant rats by enzyme digestion. The luteal cells were mixed with cytodex 3 microcarrier beads (1 mg/ml PBS) coated with laminin (0.1 mg/ml). These anchorage dependent cells in medium 199 were placed in equal numbers in a high aspect ratio vessel (HARV) bioreactor at a speed of 3 rpm and in a spinner flask control vessel. The culture vessels were placed in an incubator supplied with 5% CO₂ and 95% air. Microgravity (bioreactor) reduces the daily production of P day 1 through 8 (2.95±0.8 vs 22.16±2.65 ng/ml in control on day 3).  Cells remained viable and attached to the beads throughout the experiment as visualized by the scanning electron microscopy. Cells plated in slide flasks and subjected to microgravity using a clinostat (where there is no free fall of cells as in the bioreactor) yielded similar results when compared to their stationary controls placed in the same incubator (1.61 vs 2.70 ng/ml of P at 48 h of culture).  Further, when they were stained by oil red for lipid droplets, the clinostat flasks showed a higher percentage of stained cells compared to control flasks at 48 h (28.48 vs 20.90).  Also, the relative amount of oil red staining/mg protein was found to be higher in the clinostat than the control cells at 48 h (18.36 vs 6.13). The increase in the level of lipid content in cells subjected to microgravity may be due to a disruption in cholesterol transport and/or lesions in the steroidogenic pathway leading to a fall in the synthesis of P.  Additionally, the fall in P in microgravity conditions may be due to apoptosis in luteal cells similar to earlier published observations for lymphocytes (Lewis et al. 1998). This is currently being investigated. 

(Supported by NASA: NAG9-963 to RS).

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