David Cool (Advisor)
Master of Science (MS)
Endocrine glands secrete peptide hormones that bind to specific receptors, and elicit a response. In the pituitary, prohormone convertases (PC) PC1/3 and PC2 convert inactive prohormones into biologically active peptide hormones. Proopiomelanocortin (POMC) is a precursor molecule that proteolytically cleaves at paired basic residue sites, and produces smaller biologically active peptides, such as adrenocorticotropic hormone (ACTH), α-melanocyte stimulating hormone (α-MSH), and β-endorphin. β-endorphin is an endogenous opioid peptide hormone that plays a vital role in the body's physiological response to stress, fear, and anxiety. Morphine is an exogenous opioid, used for the treatment of moderate to severe pain and competes with β-endorphins when binding to mu-receptors located on the surface of target cells. Opioids have a high abuse potential leading to the development of tolerance and dependence. The purpose of this research is to analyze the effects of morphine on prohormone processing by examining the β-endorphin peptide hormone spectrum using a Protein Chip Array technology with Surface Enhanced Laser Desorption Ionization Time of Flight Mass Spectrometry (SELDI- TOF-MS). Brain extracts (amygdala, nucleus accumbens, periaqueductal gray, lateral hypothalamus, arcuate nucleus, and paraventricular nucleus) from normal rats (n= 4-6) treated with morphine (75mg/day) or placebo pellet for 24 hours or a seven day treatment were examined in this study. The protein (1ug/uL) was applied to a Weak Cation Exchange (WCX2) ProteinChip, air-dried, and coated with alpha-cyano-4-hydroxy cinnamic acid (CHCA) matrix. SELDI-TOF MS (Ciphergen, LaJolla, CA) was used to analyze the peptide hormone spectrum for changes in peptide expression or processing levels. The results showed that morphine modulates β-endorphin processing at 7 days. Previous studies have shown that PC2 enzyme is primarily responsible for processing β-endorphin1-31 in mice. We conclude that PC2 is down-regulated, which may play a role in regulating the amount of active hormone to prohormone. This process may help the organism maintain homeostasis.
Department or Program
Department of Pharmacology and Toxicology
Year Degree Awarded
Copyright 2007, all rights reserved. This open access ETD is published by Wright State University and OhioLINK.