Circulating interleukin-1b levels after acute and prolonged exposure to low temperatures. Human and rat studies.

In this study we have investigated whether IL-1 acts as a mediator of stress responses elicited by exposure to low temperatures. We also sought whether IL-1 is released from the adrenal gland under basal conditions or after exposure to low temperatures. Normal and adrenalectomized (ADX) rats were used for acute studies, whereas the effects of a prolonged exposure were investigated in a group of human subjects during a 45-day stay in Antarctica. Circulating levels of interleukin-1beta (IL-1beta) were taken as a marker of systemic IL-1 production both in humans and rats. In the latter, serum corticosterone (Cort) was also estimated. In intact rats, exposure to low temperatures (-25 or -35 degrees C) for 30 or 90 min did not modify circulating IL-1beta levels with respect to controls taken at +20 degrees C. Adrenalectomy was associated with an increase in cytokine levels only in the group exposed to -35 degrees C for 90 min; such increase is statistically significant compared to all groups of normal rats, whatever the experimental condition, as well as to ADX rats exposed to +20 degrees C and -25 degrees C for 30 and 90 min. In normal rats, the increase in circulating Cort levels was already maximal after exposure to -25 degrees C for 30 min. In humans, circulating IL-1beta levels after 45 days in Antarctica were significantly lower than those measured on arrival in the same subjects. Thus, no change in circulating IL-1beta was associated with acute low-temperature stress in rats, whereas a marked decrease in serum cytokine was observed in humans after prolonged exposure to a cold environment. Experiments with ADX rats indicated that the contribution of the adrenal glands to total-body IL-1beta production is negligible or absent.