Characterization of humoral endorphin

Area of Science:

• Neuroscience
• Endocrinology
• Biochemistry

Background:

• Endorphins are endogenous opioid peptides with diverse physiological roles.
• Previous studies have focused on endorphins within the central nervous system.

Purpose of the Study:

• To characterize humoral endorphin in various body fluids and tissues.
• To investigate the stability and biological activity of humoral endorphin.
• To examine changes in humoral endorphin levels during pregnancy.

Main Methods:

• Radioimmunoassay (RIA) using anti-leu-enkephalin antibodies.
• Trichloroacetic acid (TCA) pretreatment for immunoreactivity detection.
• Opiate receptor assay.
• Gel filtration chromatography (Bio-Gel P-2, Sephadex G-10).
• High-performance liquid chromatography (HPLC) of rat brain homogenate.
• Incubation studies in cerebrospinal fluid (CSF) and blood.
• Guinea pig ileum contraction assay with naloxone reversal.

Main Results:

• Humoral endorphin was detected in cerebrospinal fluid (CSF), amniotic fluid (AF), and blood, requiring TCA pretreatment for RIA detection.
• Gel filtration indicated a molecular weight of 1,000-1,400 daltons for humoral endorphin in human fluids.
• Rat brain chromatography revealed two immunoreactive peaks, one likely enkephalins and the other humoral endorphin.
• Humoral endorphin exhibited stability in CSF but faster degradation in blood.
• The opioid compound inhibited electrically stimulated guinea pig ileum contractions, reversible by naloxone.
• Maternal and cord blood endorphin levels remained stable during pregnancy.
• Amniotic fluid showed significantly higher humoral endorphin concentrations at mid-trimester compared to term pregnancies during labor.

Conclusions:

• Humoral endorphin is present in various body fluids and possesses opioid activity.
• Its molecular size and stability vary depending on the biological matrix.
• Pregnancy influences amniotic fluid endorphin levels, suggesting a role in fetal development or maternal-fetal signaling.