Uncoupling Protein mRNA Expression during the Perinatal Period of the Rat

Abstract

Brown adipose tissue is specialized in thermogenesis and it is considered as a major site for heat production in newborn mammals as well as in cold-adapted or overfed adult rodents. The thermogenic function of brown fat is the result of the presence of the “uncoupling protein” (UCP), present in the inner mitochondrial membrane. This protein short-circuits the proton electrochemical gradient generated by the respiratory chain activy as a natural uncoupler of oxidative phosphorylation (1). UCP is unique to brown fat and can be considered as a cell marker of brown adipocytes. Recently, a molecular approach to UCP has been developed in several laboratories by isolating UCP cDNAs for rat, mouse, lamb and bovine as well as specific genomic probes for human and ovine UCP. These cDNAs have been used to determine the sequence of UCP which has revealed a striking structural homology with other mitochondrial membrane proteins such as the ADP/ATP carrier or the phosphate carrier. The use of molecular probes as tools to monitor UCP mRNA levels in adult animals has shown that changes in the thermogenic activity of brown fat parallel UCP mRNA levels in the tissue, whereas run-on transcription experiments with isolated brown fat nuclei have established a main transcriptional control of UCP synthesis (for review see 2).