Alpha-melanocyte-stimulating hormone and N-acetyl-beta-endorphin immunoreactivities are localized in the human pituitary but are not restricted to the zona intermedia.

The adult human pituitary lacks a well defined intermediate lobe, and it is uncertain whether the POMC cells that remain in the zona intermedia represent melanotropes or corticotropes. In the present study, we investigated whether the N-acetylated beta-endorphin- and alpha-MSH-related peptides that are characteristically produced by melanotropes in the rat and other species are localized in the human pituitary. Sequential gel filtration and ion exchange HPLC analysis revealed that small amounts of alpha-N-acetyl-beta-endorphin-(1-31), as well as beta-endorphin-(1-27) and beta-endorphin-(1-26), were detectable in human pituitary extracts, although beta-endorphin-(1-31) was clearly the major form. Consistent with this analysis, low levels of alpha-MSH, but not N,O-diacetyl-alpha-MSH, were identified by reverse-phase HPLC, although again, the desacetyl form of alpha-MSH predominated. Immunohistochemistry revealed that N-acetyl-beta-endorphin immunoreactivity was colocalized with ACTH and beta-endorphin in a subpopulation of zona intermedia cells. Unexpectedly, immunoreactive N-acetyl-beta-endorphin was also observed in a comparable proportion of corticotropes dispersed throughout the anterior lobe. alpha-MSH immunoreactivity was similarly distributed. These results indicate that N-acetylation is not restricted to the zona intermedia, suggesting that the strict dichotomy between corticotrope and melanotrope POMC processing observed in the rat and other species does not extend to the human pituitary.

Localization of neuropeptide Y immunoreactivity and [125I]peptide YY binding sites in the human pituitary.

High levels of neuropeptide Y (NPY) are found in the hypothalamus, median eminence, pituitary portal blood, and the pituitary in a number of species. Neuropeptide Y may influence the synthesis and secretion of a variety of hormones by interacting with specific receptors in the hypothalamus and/or the pituitary. To further define the function of NPY in the pituitary, we have examined the distribution of NPY immunoreactivity and NPY receptors in sections of human pituitary using immunohistochemical and autoradiographic techniques. Neuropeptide Y-immunoreactive varicose axons were seen throughout the neural lobe. A moderate number of NPY-immunoreactive cells were found in the anterior lobe. A very high level of [125I]PYY binding was seen in the neural lobe with low levels in the anterior lobe. The binding in the neural lobe was inhibited by NPY(13-36) at a Ki of 5.3 nM and [Leu31-Pro34]NPY at a Ki of 390 nM, indicating the receptor was the Y2 subtype. Therefore, neuronally released NPY may modulate human neural lobe function through a Y2 receptor.

Radiographic assessment of traumatic rupture of the thoracic aorta.

The authors discuss the advantages and limitations of radiographic modalities in assessing traumatic rupture of the thoracic aorta (TRTA). TRTA is one of the most frequent causes of death from high-speed deceleration accidents and other blunt trauma sustained during motor vehicle accidents.

POMC-derived peptide immunoreactivity in neural lobe axons of the human pituitary.

The efferent projections of proopiomelanocortin (POMC) neurons in the arcuate nucleus and nucleus of the solitary tract have been extensively characterized in the rat, but are less well understood in the human brain. We report here that ACTH, alpha-MSH, beta-endorphin, and N-acetyl-beta-endorphin immunoreactive axons are localized in the neural lobe of the human pituitary gland, in congruence with prior evidence that beta-endorphin and other POMC-derived peptides modulate vasopressin and oxytocin secretion.