Demonstration of desacetyl α-melanocyte-stimulating hormone in fetal and adult human anterior pituitary corticotrophs

Abstract

ABSTRACT Immunocytochemistry, radioimmunoassay and high-performance liquid chromatography (HPLC) techniques have been used in combination to investigate the presence of immunoreactive (ir)-α-MSH in the normal human pituitary gland, and to investigate the possible origin of these cells from the fetal pars intermedia. Two separate antisera to α-MSH were employed in immunocytochemistry to distinguish between authentic α-MSH and the desacetyl form. Only desacetyl α-MSH was detected in the pituitary gland of fetal and adult man, in both the pars (zona) intermedia and the pars anterior. In the fetus, a large proportion of the ACTH-containing cells of the anterior lobe also contained ir-α-MSH, while ir-α-MSH containing cells were more sparse in adults. Radioimmunoassay of acid extracts of adult pituitary tissue showed α-MSH levels representing less than 0·05% of the ACTH content of the gland. HPLC analysis of these extracts confirmed that only the desacetyl form was present. These results suggest that α-MSH peptides are synthesized by anterior lobe cells of the human pituitary gland, which are not derived from the fetal pars intermedia. Possible regulatory mechanisms affecting cells which contain ir-α-MSH are discussed, and by comparison with the intermediate lobe of other species it is concluded that there is little evidence for a true intermediate lobe in the human pituitary gland. Journal of Endocrinology (1989) 120, 525–530