Mammary metabolic activity in pregnant rats is significantly increased in response to spaceflight. To determine whether changes in mammary metabolism are related to gravity load, we exposed pregnant rats to hypergravity and measured mammary metabolic activity. From day 11-20 of gestation, animals were centrifuged (20 RPM; 1.5, 1.75 or 2.0 X gravity) or were maintained at 1-g. On gestation day 20 (G20), 5 rats from each group were removed from the centrifuge and euthanized (G22). The remaining dams (N=5/treatment) were housed at 1-g until parturition. After 2 h of nursing by the pups, the post-partum dams were euthanized. Glucose oxidation to CO₂ and incorporation into lipids was measured. Mammary glands from dams euthanized on G20 revealed a strong negative correlation between metabolic rate and increased g-load. Approximately 98% of the variation in glucose oxidation and 94% of the variation in glucose incorporation into lipids can be accounted for by differences in g-load. Differences in metabolic activity disappeared in the post-partum dams. When we combined previous data from the microgravity with hypergravity environments and plotted the ratio of mammary metabolic rate versus g-load, there was a significant exponential relationship (r² = .99). These data demonstrate a remarkable continuum of response across the microgravity and hypergravity environments and support the concept that gravitational load influences tissue metabolism.