Peptide E and its products, BAM 18 and Leu-enkephalin, in bovine adrenal medulla and cultured chromaffin cells: release in response to stimulation.
Peptide E is a 25 amino acid opioid peptide which, if cleaved at the sole double basic (Lys-Arg) typical processing site, would generate two opioid fragments, the amino-terminal fragment BAM 18 and the carboxy-terminal fragment Leu-enkephalin. We have analysed extracts of bovine adrenal medulla in order to quantify these three opioid peptides (peptide E, BAM 18, and Leu-enkephalin). Here we present evidence that BAM 18 and Leu-enkephalin were present in similar amounts, whereas peptide E was present at a higher concentration. This is consistent with previous observations showing a preferential accumulation of larger peptides in the bovine adrenal, and also with the Lys-Arg bond being the principal site of cleavage of peptide E. However, when bovine adrenal chromaffin cells were maintained in culture for several days, Leu-enkephalin was found to be present in much greater amounts than was BAM 18-like immunoreactivity. The molar amounts of peptide E still exceeded the estimated levels of BAM 18 and Leu-enkephalin. We provide evidence that under conditions of basal release BAM 18 and peptide E were released, whereas Leu-enkephalin was released in much smaller amounts, if at all. On stimulation with nicotine results were consistent with an increased release of all three peptides with a preferential stimulation of Leu-enkephalin release. Under all conditions, the molar amounts of peptide E released apparently exceeded that of the other peptides. The results are discussed in terms of the regulation of partial proteolysis and the fate of peptide E.
Boarder
M R
MR
Department of Pharmacology and Therapeutics, University of Leicester, England.
Evans
C
C
Adams
M
M
Erdelyi
E
E
Barchas
J D
JD
D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D002838:Chromaffin System / Q000187:drug effects / Q000378:metabolism*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D004743:Enkephalin, Leucine / Q000378:metabolism*; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives* / Q000378:metabolism; D004745:Enkephalins; D009538:Nicotine / Q000494:pharmacology; D010446:Peptide Fragments / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D011498:Protein Precursors / Q000378:metabolism*; D011863:Radioimmunoassay
D004745:Enkephalins; D010446:Peptide Fragments; D010455:Peptides; D011498:Protein Precursors; C053492:BAM 18P; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D009538:Nicotine; C039933:peptide E (adrenal medulla); D011188:Potassium