title: Estrogen decreases rat hypothalamic proopiomelanocortin messenger ribonucleic acid levels.
abstract: Ovariectomy and estrogen (E) or E plus progesterone treatment has previously been shown to alter both hypothalamic content and portal plasma levels of beta-endorphin. To determine if these changes were accompanied by changes in beta-endorphin synthesis, we used a RNA dot blot method to quantify proopiomelanocortin (POMC) mRNA levels in the arcuate nucleus-median eminence region of rats. Animals were bilaterally ovariectomized, implanted with Silastic capsules containing E or oil, and killed 1 or 3 days after implantation. Total nucleic acid was isolated from dissections of the arcuate-median eminence by proteinase-K/sodium dodecyl sulfate/phenol extraction, and POMC mRNA was quantified by dot blot analysis. Although 1 day of E treatment had no effect on hypothalamic POMC mRNA levels, 3 days of E treatment caused a significant reduction of approximately 40% of POMC mRNA levels relative to oil controls in two replicate experiments. These results suggest that the decreases in hypothalamic POMC peptide levels after E administration reported previously may be due to a decrease in POMC peptide biosynthesis resulting from a decrease in hypothalamic POMC mRNA.
authors.forename: J N
authors.initials: JN
authors.lastname: Wilcox
authors.forename: J L
authors.initials: JL
authors.lastname: Roberts
mesh_terms: D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000032:analysis; D003692:Delayed-Action Preparations; D004723:Endorphins / Q000096:biosynthesis; D004967:Estrogens / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D007031:Hypothalamus / Q000187:drug effects* / Q000378:metabolism; D008473:Median Eminence / Q000032:analysis; D009693:Nucleic Acid Hybridization; D010052:Ovariectomy; D011333:Pro-Opiomelanocortin / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin
chemical_list: D003692:Delayed-Action Preparations; D004723:Endorphins; D004967:Estrogens; D012333:RNA, Messenger; D001615:beta-Endorphin; D011333:Pro-Opiomelanocortin