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EFFECTS OF HYPERGRAVITY (2-g) ON MAMMARY, LIVER AND ADIPOSE TISSUES IN LATE GESTATION RATS. E. I. Zakrzewska¹, R. Maple¹, L. Lintault¹, A. Ronca², C. Wade², L. Baer², K. Coughlan¹, and K. Plaut¹, ¹Dept of Animal Science, University of Vermont, Burlington, VT.  ²Life Sciences Division, NASA Ames Research Center, Moffett Field, CA.

   In previous studies we found that hypergravity decreased mammary metabolic activity in late gestation rats. To determine whether this response was specific to the mammary tissue or was the result of a homeostatic set point change that affected other tissues, we measured the metabolic activity of liver, adipose and mammary tissues in rats that were exposed to hypergravity. In this study, sixteen pregnant rats were randomly divided into hypergravity (HG) and stationary control (SC) groups.  HG dams were maintained on the centrifuge at 2-g from day 11 through day 20 of gestation (G20). SC dams were housed in identical cages. Water and feed were provided ad libitum. Adipose, mammary and liver tissues were collected from anesthetized animals, sliced 0.5 mm thick, and incubated in 37^oC for 2, 3 and 4 hrs respectively in Krebs-Ringer Buffer containing U-¹⁴C-glucose as a tracer. Glucose oxidation to ¹⁴CO₂ and incorporation of glucose to fatty acids in mammary, liver and adipose tissues were measured. Results were expressed as nmol of glucose utilized per 100 mg of wet tissue. Hypergravity significantly altered mammary metabolism in 20-day-pregnant females. Oxidation of glucose to ¹⁴CO₂ in mammary was 610 nmol /100 mg in HG group and 823 nmol/100mg in SC group (SEM = 56, p = 0.02). Incorporation of glucose to fatty acids decreased in HG (59 nmol/100mg) when compared with SC (206 nmol/100mg SEM = 25 and p = 0.001).  Glucose metabolism in adipose of G20 HG dams was not affected significantly. Glucose utilization in liver tissue was not altered. We conclude that hypergravity decreases mammary tissue metabolism relative to other tissues indicating a possible change in homeorhetic set points.

(Supported by: NASA: NCC2-1373 and NASA-EPSCoR: NCC5-581)