ACTH, β-Lipotropin, and Related Peptides in Brain, Pituitary, and Blood

Publisher Summary This chapter presents the demonstration of a precursor molecule containing adrenocorticotropic hormone (ACTH) and β -lipotropin in multiple tissues, which has the potential to be processed into products both similar to and different from those elaborated by the anterior and intermediate pituitary lobes. This has raised a number of fundamental questions with regard to its biosynthetic pathways and regulation and to the functions of the peptide products. The chapter discusses the nature and regulation of extrapituitary form of ACTH family of peptides and the forms secreted by human pituitary, both in normal subjects and in diseases characterized by disorders of ACTH regulation. Both ACTH and β -lipotropin can serve as precursors for other biologically active peptides. In humans, ACTH and β -melanotropin ( β -MSH) are secreted concomitantly and occur within the same cell of the anterior pituitary. The distribution of ACTH and β -lipotropin cells is identical. Within the arcuate nucleus, these cells in colchicine-treated rats are distributed throughout its rostrocaudal extent as for α -MSH in the vinblastine-treated rat. The concept of a hypothalamic center distributing ACTH, α -MSH, or β -endorphin via axons to regulate many other brain regions is comparable to the oxytocin and vasopressin fibers in many extra hypothalamic sites that originate in the magnocellular paraventricular nucleus of the hypothalamus. The ACTH- β -lipotropin and vasopressin-oxytocin systems are unique among known brain peptides as their perikarya is restricted to the hypothalamus. The hypothalamus is the center of the ACTH- β -lipotropin brain.