Circulating interleukin-1-beta 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 stres s responses elicited by exposure to low temperatures. We also sought whethe r IL-1 is released from the adrenal gland under basal conditions or after e xposure to low temperatures. Normal and adrenalectomized (ADX) rats were us ed for acute studies, whereas the effects of a prolonged exposure were inve stigated in a group of human subjects during a 45-day stay in Antarctica. C irculating levels of interleukin-1 beta (IL-1 beta) were taken as a marker of systemic IL-1 production both in humans and rats. In the latter, serum c orticosterone (Cort) was also estimated. In intact rats, exposure to low te mperatures (-25 or -35 degrees C) for 30 or 90 min did not modify circulati ng IL-1 beta levels with respect to controls taken at +20 degrees C. Adrena lectomy was associated with an increase in cytokine levels only in the grou p exposed to -35 degrees C for 90 min; such increase is statistically signi ficant compared to all groups of normal rats, whatever the experimental con dition, as well as to ADX rats exposed to +20 degrees C and -25 degrees C f or 30 and 90 min. In normal rats, the increase in circulating Cort levels w as already maximal after exposure to -25 degrees C for 30 min. In humans, c irculating IL-1 beta levels after 45 days in Antarctica were significantly lower than those measured on arrival in the same subjects. Thus, no change in circulating IL-1 beta was associated with acute low-temperature stress i n rats, whereas a marked decrease in serum cytokine was observed in humans after prolonged exposure to a cold environment. Experiments with ADX rats i ndicated that the contribution of the adrenal glands to total-body IL-1 bet a production is negligible or absent. Copyright (C) 2000 S. Karger AG. Base l.