α1-Antitrypsin (AT), the archetypal member of the superfamily of serine proteinase inhibitors, inhibits leukocyte elastase activity and thereby can prevent lung damage. Here we show that in fibroblasts from human fetal lung and mouse embryo as well as in certain epithelial cells AT can also enhance the stimulatory effects of insulin on DNA synthesis and cell proliferation. Warming of AT at a moderate (41°C) temperature for a longer time (21 h) or at a higher (65°C) temperature for 30 min before treatment increased its stimulatory effects on both DNA synthesis and activating phosphorylation of p42/p44 mitogen-activated protein kinases. The results suggest that AT may promote regeneration of damaged tissues under pathophysiological conditions which are associated with fever.
