Demonstration of desacetyl alpha-melanocyte-stimulating hormone in fetal and adult human anterior pituitary corticotrophs.
Immunocytochemistry, radioimmunoassay and high-performance liquid chromatography (HPLC) techniques have been used in combination to investigate the presence of immunoreactive (ir)-alpha-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 alpha-MSH were employed in immunocytochemistry to distinguish between authentic alpha-MSH and the desacetyl form. Only desacetyl alpha-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-alpha-MSH, while ir-alpha-MSH containing cells were more sparse in adults. Radioimmunoassay of acid extracts of adult pituitary tissue showed alpha-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 alpha-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-alpha-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.
Coates
P J
PJ
Department of Histopathology, St Bartholomew's Hospital, West Smithfield, London.
Doniach
I
I
Holly
J M
JM
Rees
L H
LH
D000328:Adult; D002851:Chromatography, High Pressure Liquid; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D010446:Peptide Fragments / Q000032:analysis*; D010903:Pituitary Gland, Anterior / Q000032:analysis* / Q000033:anatomy & histology / Q000196:embryology; D011863:Radioimmunoassay; D000521:alpha-MSH / Q000031:analogs & derivatives* / Q000032:analysis
D010446:Peptide Fragments; D000521:alpha-MSH