Peptides related to α-melanocyte-stimulating hormone are commonly produced by human pituitary corticotroph adenomas: no relationship with pars intermedia origin

Abstract

The presence of immunoreactive (ir)-alpha-MSH has been investigated by immunocytochemistry in 24 pituitary adenomas and one case of corticotroph hyperplasia causing Cushing's disease, in four adenomas causing Nelson's syndrome, and in ten 'silent' corticotroph adenomas. It was found that a high proportion of these adenomas have a population of cells containing ir-alpha-MSH in addition to ir-ACTH. In some instances, these adenomas were clearly not associated with the residual intermediate lobe of the pituitary. Radioimmunoassay of plasma from patients with Cushing's disease or Nelson's syndrome showed elevated levels of ir-alpha-MSH in the majority of cases. Characterization of the ir-alpha-MSH in adenoma cells by immunocytochemistry, using an antiserum selective for acetylated forms of alpha-MSH, suggested that only the desacetyl form was present in each case examined. High-performance liquid chromatography of adenoma tissue extracts revealed material co-eluting with acetylated forms of alpha-MSH in only one of six cases. These results have been compared with corticotroph adenomas in animal pituitary glands, and it is concluded that the presence of alpha-MSH peptides cannot be used as a marker for intermediate lobe tumours, and that desacetyl alpha-MSH is commonly produced by corticotroph adenomas.

In vivo and in vitro Studies in a Patient with Cyclical Cushing’s Disease Showing Some Responsiveness to Bromocriptine

“…ACTH to IR p-END (p-LPH + p-END) molar ratios were 0.85 in the adenoma and 0.83 in the tissues indicated that the adenoma contained more than 25 times higher IR a-MSH than the surrounding tissues. The level in the adenoma (5.0 ng/mg wet weight) was similar to what was previously reported for corticotroph adenomas (5,200 ± 2, lOOng/g wet weight; mean ± SEM) [5], Concentrations of the other anterior pituitary hormones in the surrounding tissues (expressed as per milligram wet weight) were 930 ng for GH. 360 ng for PRL.…”

“…Indeed, accumu lating morphological [5. 19-22] and biochemical [5,23] studies have proposed that the Lamberts' hypothesis should not be accepted or. at least, should be revised.…”

Pituitary-dependent hyperadrenocorticism in a family of Dandie Dinmont terriers

“…With regard to this latter possibility data have been presented suggesting that adrenocorticotrophic hormone-secreting pitu¬ itary adenomas may originate from either the anterior lobe or intermediate-lobe remnants (Lamberts, De Lange & Stefanko, 1982;Lamberts, 1987). The 'intermediate-lobe hypothesis' has been criticized on the basis of clinical studies (Koppeschaar, Croughs, Thijssen & Schwarz, 1986;Pieters, Smals, Goverde et al 1982) and morphological observations (McNicol, Teasdale & Beastall, 1986;Coates, Doniach, Hale & Rees, 1986;Coates, Doniach, Wells et al 1989).…”

A Case Report of Invasive Pituitary Tumors Containing Alpha-Melanocyte-Stimulating Hormone Arising from the Pars Distalis in F344 Rats

“…Tumor cells containing a.-MSH of the pars distalis have been previously described in humans and dogs with Cushing's disease (3,6,8,9,11). In the rat pituitary tumor, however, cells containing a-MSH have not been verified so far.…”

“…Submissions will be reviewed for clarity and relevance to the journal readership. Comments (3,6,8,9,11 For immunohistochemical detection of a-MSH, prolactin (PRL), and proliferating cell nuclear antigen (PCNA), selected tissue sections were processed by a labeled streptavidin-biotin (LSAB) method. In brief, the paraffin section was deparaffinized, treated sequentially with rabbit anti-a-MSH antibody (1:500, Biogenesis, Inc, NH), rabbit anti-rat prolactin antibody (1:1,000, Chemicon International Co, Ltd, CA), or mouse anti-PCNA antibody (1:100, DAKO Japan Co., Ltd., Tokyo, Japan) as the primary antibody, followed by staining with an LSAB kit (DAKO Japan Co, Ltd …”