Distribution of endorphins (peptides with morphine-like pharmacological activity) in pituitary

Endorphin was found in the pituitary gland of rat, sheep, pig, cow and man. In bovine pituitary, highest concentrations have been found in that part of the posterior lobe containing the pars intermedia, although endorphin was also present in the pars distalis. Analysis by gel filtration and adsorption chromatography suggested that the major endorphins from rat, pig and cow pituitary were similar, with apparent molecular weights in the range 3000-3500 daltons.