Endotoxin-stimulated opioid peptide secretion: two secretory pools and feedback control in vivo.
Small doses of endotoxin evoked a dramatic biphasic response of opioid peptide secretion into blood in sheep. The first phase began within minutes and coincided with a brief hypertensive response to endotoxin well before the appearance of fever or hypotension. The ratio of beta-endorphin to beta-lipotropin fell abruptly at the onset of the second phase of release, suggesting early depletion of a pool rich in beta-endorphin and subsequent emergence of a pool rich in unprocessed precursor. The concentration of cerebrospinal fluid opioids increased tenfold during the second phase. Naloxone administration augmented endotoxin-induced opioid secretion in both early and late phases, suggesting a short-loop feedback regulation of stress-induced endorphin secretion.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004723:Endorphins / Q000097:blood / Q000134:cerebrospinal fluid / Q000378:metabolism*; D004731:Endotoxins / Q000494:pharmacology*; D004926:Escherichia coli; D005246:Feedback; D007700:Kinetics; D009270:Naloxone / Q000494:pharmacology; D010446:Peptide Fragments / Q000097:blood / Q000134:cerebrospinal fluid; D012756:Sheep; D001615:beta-Endorphin
D004723:Endorphins; D004731:Endotoxins; D010446:Peptide Fragments; D009270:Naloxone; D001615:beta-Endorphin; C018903:gamma-endorphin, des-Tyr(1)-