Endotoxin-induced formation of specific beta-endorphin binding sites in human serum.

Specific binding of human beta-endorphin is demonstrated to sites that are present in endotoxin-treated, but not in native, human serum. Binding is saturable and reversible and is mediated by a nonopioid segment of beta H-endorphin to sites that are located on the terminal SC5b-9 complement complex. Since endotoxemia causes both the secretion of beta-endorphin into blood (1) and the formation of specific beta-endorphin binding sites therein, both effects might be elements of a common physiological process.