Two pools of beta-endorphin-like immunoreactivity in blood: plasma and erythrocytes.
While attempting to delineate the reason for the reported extreme variability of beta-endorphin-like immunoreactivity (beta-ir) in human plasma (eg., nondetectable to 1 ng/ml) by standard radioimmunoassay, we noted that a substantial portion of circulating beta-ir was associated with erythrocytes. That erythrocyte associated beta-ir is authentic beta-endorphin (beta-EP) was confirmed by high performance liquid chromatography (HPLC). Analysis of blood samples from rabbits, rats and mice revealed the presence of beta-ir in erythrocytes from these species as well. These results suggest that there are two pools of beta-endorphin-like immunoreactivity in blood: plasma and erythrocytes.
D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D004533:Egtazic Acid / Q000494:pharmacology; D004723:Endorphins / Q000097:blood*; D004912:Erythrocytes / Q000032:analysis*; D006801:Humans; D051379:Mice; D009994:Osmolar Concentration; D011817:Rabbits; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin
D004723:Endorphins; D004533:Egtazic Acid; D001615:beta-Endorphin; D002122:Calcium Chloride