Presence of met-enkephalin in bovine pituitary intraglandular colloid of intermediate lobe origin

Met-enkephalin, and opioid peptide present in the intermediate lobe of the pituitary gland, is herein demonstrated, for the first time, in bovine pituitary intraglandular colloid. Colloid samples were taken from the glands of freshly slaughtered cattle, pooled, lyophilized, extracted on octadecylsilyl-silica and assessed by radioimmunoassay. Met-enkephalin was indeed present in this colloid extract at levels varying from 0.40 to 0.85 nanograms per milligram dry weight. Locating an intermediate lobe peptide in intraglandular colloid is a significant finding since this implies that colloid, housed in the intraglandular lumen, may serve as a transport medium. Intermediate lobe peptides which, because the intermediate lobe is avascular, are otherwise denied the vascular transport routes available to the anterior and posterior lobe hormones.