The "second messenger" system in brown adipose tissue of developing rats. Its molecular composition and mechanism of function.

Our studies of the hormonal receptor system and of the sequence of enzymatic events interconnecting the initial hormonal stimulus to the brown adipocyte with its final subcellular effect are summarized here. The hormone-mediated regulatory pathway consists of the adenyl cyclase and the protein kinase systems; the former is composed of the receptor and catalytic sites, the latter of regulatory and catalytic subunits. Emphasis is given currently to the diversity and characteristics of the individual components of the protein kinase system, since it seems to carry out the ultimate unifying mechanism involved in a variety of hormone-mediated functions, i.e. the phosphorylation of a protein molecule.