METABOLIC-RATE AND NITROGEN-BALANCE AFTER SKELETAL TRAUMA IN FEMALE AND MALE-RATS

Unequal metabolic responses to trauma by women and men have been sugge sted, but an explicit investigation demonstrating this conjecture has not been made. The responses of resting energy expenditure (REE) and n itrogen balance for 3 days before and 7 days after skeletal trauma wer e determined for female and male rats. Food intake and body weight wer e recorded daily, and 24-h urine samples were collected. Baseline REE and nitrogen balance were obtained for 3 consecutive days before induc tion of trauma. Then rats were divided into female trauma (n = 8), mal e trauma (n = 7), female control (n = 8), and male control (n = 7) gro ups. Trauma was produced by bilateral femoral fracture to anesthetized rats. Control rats were anesthetized without skeletal trauma. Traumat ized rats were fed ad libitum for 7 days, and control rats were pair f ed with the traumatized rats. The results showed that REE increased an d nitrogen balance decreased in traumatized male rats relative to thei r controls. Traumatized female rats had increased REE and unchanged ni trogen balance compared with their controls. Traumatized female rats h ad a larger percentage increase in REE on days 5 through 7 than did tr aumatized male rats. These findings demonstrate a difference between f emale and male rats in response to trauma. Female rats use more energy and lose less nitrogen after trauma than do male rats. The results su ggest that recommendations for increased energy and protein needs afte r trauma should consider the sex of the subject intended to be fed.