Presence of immunoreactive β-lipotropin and β-endorphin in human placenta

Utilizing a sensitive radioimmunoassay capable of detecting both β-lipotropin (β-LPH) and β-endorphin (β-EP), we demonstrated the existence of immunoreactive β-LPH and β-EP in extracts of human placentas. Gel chromatographic studies revealed that total β-EP immunoreactivity consists of two fractions with elution positions compatible with β-LPH and β-EP, respectively, and a fraction of larger molecular weight. All three fractions showed parallel curves with the standard curve of β-EP in radioimmunoassay. Our observations suggests that β-EP, β-LPH and possibly their precursor exist in human placenta.