Endotoxin‐induced hyperthermia in pregnant golden hamsters

The degree of elevation and the duration of induced fever following endotoxin treatment of pregnant golden hamsters were examined. A radiothermistor was surgically implanted in the abdomen of each animal on day 6 of pregnancy. The animals were intravenously treated with a bolus injection of saline or endotoxin (1, 10, 20, or 200 micrograms/kg) on the morning of day 8 of gestation. Abdominal temperatures were monitored at 15-minute intervals on days 8 and 9 and at 1-hour intervals on days 10 through 14 of gestation. The mean temperature of the saline-treated control animals was 37.2 degrees C with a range from 36.5 to 38.2 degrees C. The total number of viable fetuses, and the mean fetal weight of the 1-microgram/kg group were not significantly different from those of the saline controls, although a statistically significant monophasic temperature elevation did occur between 3 and 9 hr post-treatment. Three of seven females that received 10 micrograms/kg had viable litters and exhibited a monophasic fever. The remaining four animals exhibited a biphasic fever and total resorption of all implanted fetuses. The first phase began 2.5 hr post-treatment and lasted for 3-6 hr. The second phase began 12-15 hr post-treatment and lasted for 15 to 25 hr. All animals receiving 20 or 200 micrograms/kg demonstrated similar multiple temperature elevations. Treatment of animals with greater than 20 micrograms/kg resulted in total resorption of all implanted fetuses and maternal weight loss. Nonpregnant females treated with 20 micrograms/kg of endotoxin exhibited a biphasic temperature elevation; thus the second phase of the fever response can not be attributed to embryo death and resorption.