['To determine the effects of polymyxin B sulfate in rats fed by total parenteral nutrition on norepinephrine excretion, macrophage tumor necrosis factor production, and bacterial translocation.', 'Randomized animal study.', 'A university teaching hospital in Seattle, Wash.', 'Three groups of rats were studied: chow plus intravenous saline, total parenteral nutrition, or total parenteral nutrition supplemented with polymyxin B sulfate. After 5 days, urinary excretion of norepinephrine and epinephrine was calculated, peritoneal and alveolar macrophages were cultured, and their spontaneous and lipopolysaccharide-stimulated tumor necrosis factor production was measured. Mesenteric lymph nodes were cultured for bacteria.', 'Rats fed by total parenteral nutrition had increased urine norepinephrine excretion (33%) and alveolar macrophage tumor necrosis factor production (80%) and trends for increased epinephrine excretion and bacterial translocation compared with rats fed chow. Alveolar but not peritoneal macrophage tumor necrosis factor production was significantly related to norepinephrine excretion (r = .5, P < .01). The addition of polymyxin B to total parenteral nutrition decreased weight gain (P < .05), urinary norepinephrine excretion (P < .01), and alveolar macrophage tumor necrosis factor production (P < .05) compared with rats fed by total parenteral nutrition. Polymyxin B also tended to decrease the magnitude of bacterial translocation.'] Does polymyxin B prevent increased sympathetic activity and alveolar macrophage tumor necrosis factor release in parenterally fed rats?