title: Evidence for a differential postnatal development of proenkephalin B (= prodynorphin)-derived opioid peptides in the rat hypothalamus.
abstract: [he concentrations of immunoreactive (ir-) peptides derived from the opioid peptide precursors proenkephalin A (Met-enkephalin), proenkephalin B [dynorphin (DYN)-(1-17), dynorphin-(1-8), dynorphin B, alpha-neoendorphin (alpha-NEO-E), beta-NEO-E] and proopiomelanocortin [beta-endorphin (beta-END)], and of the neurosecretory hormones vasopressin and oxytocin increased between approximately 10-fold and 50-fold from birth to adulthood in the rate hypothalamus. Gel filtration and HPLC analysis of proenkephalin B-derived opioid peptides revealed that in 3-day-old rats the predominant portion of ir-dynorphin-(1-17) and a substantial part of ir-dynorphin B consisted of a high (6000) mol wt species, a common precursor peptide for DYN-(1-17) and DYN B. In adults rats, however, authentic DYN-(1-17) and DYN B were found to be the major ir-forms. The mol wt patterns of ir-DYN-(1-8), ir-alpha-NEO-E and ir-beta-NEO-E did not differ between 3-day-old and adult rats and reflected predominantly the respective authentic opioid peptides. Taking into consideration the developmental changes in the mol wt pattern of ir-DYN-(1-17), authentic DYN-(1-17) was 5 times lower in concentration than DYN-(1-8) in 3-day-old rats, whereas in adults these opioid peptides occurred in equimolar concentrations. These findings suggest that the posttranslational processing of the precursor proenkephalin B changes in the course of postnatal development. Ir-beta-END in the hypothalamus of newborn and adult rats consisted exclusively of beta-END-sized peptides which were not (unlike those in the intermediate pituitary lobe) alpha-N-acetylated. Thus, in the hypothalamus, the enzymatic processing of the opioid peptide precursor proopiomelanocortin to beta-END seems to be fully active at birth, in contrast to that of proenkephalin B.
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D004745:Enkephalins / Q000378:metabolism*; D005260:Female; D007031:Hypothalamus / Q000254:growth & development*; D008297:Male; D008970:Molecular Weight; D010121:Oxytocin / Q000378:metabolism; D010908:Pituitary Hormones, Anterior / Q000378:metabolism; D011247:Pregnancy; D011333:Pro-Opiomelanocortin; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012737:Sex Factors; D014667:Vasopressins / Q000378:metabolism
chemical_list: D004745:Enkephalins; D010908:Pituitary Hormones, Anterior; D011498:Protein Precursors; D014667:Vasopressins; D010121:Oxytocin; D011333:Pro-Opiomelanocortin; C033660:preproenkephalin