Early metabolic consequences of epidermal growth factor administration to neonatal rats

Daily administration of epidermal growth factor (EGF) to neonatal rodents elicits a classic morphogenetic syndrome. In this study, we examined the early (minutes to hours) consequences of EGF treatment in the neonatal rat (age 0-72 h). Significant findings included a rapid reduction in resting heart rate 4 h after EGF treatment accompanied by a sensitive dose- and age-dependent decrease in systemic oxygen consumption (VO2). Midscapular skin temperature (MST) was measured as a putative noninvasive indicator of brown adipose tissue thermogenesis. As little as 10 ng EGF/g body wt elicited a significant reduction in MST. Both the decrease in VO2 evoked by EGF and the MST response were potentiated by environmental cold exposure. EGF treatment also resulted in rapid (90 min) reductions in circulating levels of glycerol, triglyceride, and cholesterol while increasing serum glucose and arachidonic acid. Other free fatty acids were unaffected. Serum lactate levels were increased by EGF with the same time course as the reduction in VO2. These results provide new biochemical data on the pharmacological actions of EGF and further characterize the EGF-treated neonatal rodent as an intriguing in vivo model of growth factor action.