title: Simulated weightlessness: effects of bioenergetic balance.
abstract: As a prelude to a flight experiment, an attempt was made to separate energy requirements associated with gravity from all other metabolic needs. The biological effects of weightlessness were simulated by suspending animals in a harness so that antigravity muscles were not supporting the body. Twelve pairs of rats were allowed to adapt to wearing a harness for 5 d. Experimental animals were then suspended in harness for 7 d followed by recovery for 7 d. Control animals were harnessed but never suspended. VO2, VCO2 and rate of 14CO2 expiration from radio-labeled glucose were monitored on selected days. Food intake and body mass were recorded daily. Metabolic rate decreased in experimental animals during 7 d of suspension and returned to normal during recovery. Although some of the metabolic changes may have related to variation in food intake, simulated weightlessness appears to directly affect bioenergetic balance.
mesh_terms: D000818:Animals; D001835:Body Weight; D002245:Carbon Dioxide / Q000502:physiology; D004435:Eating; D004734:Energy Metabolism; D008297:Male; D010101:Oxygen Consumption; D051381:Rats; D012119:Respiration; D013997:Time Factors; D014893:Weightlessness
chemical_list: D002245:Carbon Dioxide