Age-dependent mortality during endotoxemia. (A) A survival study demonstrating age-dependent mortality during endotoxemia. Young (4 months) and aged (24 months) male C57BL/6 mice received an intraperitoneal injection with LPS at various doses, and survival was monitored for 7 days. For each dose point, 8 to 14 mice were studied. No mortality was found in control mice with saline injection (not shown here). (B) Seven-day survival curves from the same experiment comparing mortality rates of young mice (LPS 2.5 mg/kg or 20 mg/kg) and aged mice (LPS 2.5 mg/kg). There was no statistical difference between the survival curve patterns of aged mice with 2.5 mg/kg LPS and young mice with 20 mg/kg LPS (P = .52). (C) Degree of hypothermia 12 hours after LPS injection was compared among young mice (LPS 2.5 mg/kg or 20 mg/kg) and aged mice (LPS 2.5 mg/kg). ***Statistical significance (P < .001). There was no statistical difference between body temperatures of aged mice with 2.5 mg/kg LPS and young mice with 20 mg/kg LPS (P = .54).