The Regulation of Proopiomelanocortin Gene Expression by Estrogen in the Rat Hypothalamus

Abstract

Many, if not all, neuropeptides are derived biosynthetically from larger precursor proteins. Proopiomelanocortin (POMC) is an example of such a precursor protein from which beta LPH, ACTH, the MSH’s, and beta-endorphin are derived (reviewed in Eipper and Mains, 1980). Immunohistochemical staining using ACTH or endorphin antibodies indicates that these peptides are present in cell bodies in the periarcuate region of the rat hypothalamus extending from the retrochiasmatic area to the premammilary nucleus (Bloak et al., 1979; Bloom et al., 1978; Finley et al., 1981; Joseph, 1980; Pelletier and Leclerc, 1979; Watson et al., 1978; Watkins, 1980; Zimmerman et al., 1978). It was initially thought that the POMC peptides in the brain were derived by transport and uptake of these proteins from the pituitary, a tissue rich in ACTH and beta-endorphin. However, it has recently been shown that the hypothalamus actually synthesizes POMC (Liotta et al., 1979), contains POMC mRNA (Civelli et al., 1982; Gee et al., 1983), and releases beta-endorhin into the portal blood (Wardlaw et al., 1980; Sarkar and Yen, 1984), suggesting that the hypothalamic POMC cells synthesize POMC independent of the pituitary.