Synaptophysin immunoreactivity in adrenocortical adenomas: a correlation between synaptophysin and CYP17A1 expression.
METHODS
The adrenal cortex is not considered to be an intrinsic part of the diffuse neuroendocrine system, but adrenocortical neoplasms possess neuroendocrine properties. In this study, we examined synaptophysin (SYP) and neural cell adhesion molecule (NCAM) expression in adrenocortical adenomas in relation to adrenal function.


RESULTS
Immunohistochemical analysis showed that 50.7 and 98.6% of the cortical adenomas showed SYP and NCAM immunoreactivities respectively. There was no apparent difference in NCAM immunoreactivity among the adenomas. However, the immunostaining for SYP was significantly stronger in cortisol-producing adenomas (CPA) than in aldosterone-producing adenomas (APA), nonfunctioning adenomas (NFA), showing no clinical or endocrinological abnormality, or adenomas associated with preclinical Cushing's syndrome (preCS). Western blotting and real-time PCR demonstrated that the expression level of SYP protein and mRNA was significantly higher in CPA than in APA or NFA. Additionally, the SYP mRNA level showed a positive correlation with CYP17A1 mRNA. In addition to the plasma membrane, mitochondria, and smooth endoplasmic reticulum, SYP immunoreactivity was detected in the Golgi area, which is known to be involved in the regulation of mitochondrial cholesterol and the transport of steroid intermediates. It was unexpected that the ratio of positive cells for SYP in preCS was less than that in APA and NFA. However, further examination is required, because the number of preCS cases we investigated was very small.


CONCLUSIONS
We propose that SYP expression in adrenocortical cells may be involved in some aspect of adrenal function such as transport or secretion of glucocorticoids.
Shigematsu
Kazuto
K
Department of Pathology, Japanese Red-Cross Nagasaki Atomic Bomb Hospital, Nagasaki 852-8511, Japan. shigek@nagasaki-med.jrc.or.jp
Nishida
Noriyuki
N
Sakai
Hideki
H
Igawa
Tsukasa
T
Toriyama
Kan
K
Nakatani
Akira
A
Takahara
Osamu
O
Kawai
Kioko
K
D000302:Adrenal Cortex / Q000737:chemistry*; D000310:Adrenal Gland Neoplasms / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D019006:Neural Cell Adhesion Molecules / Q000096:biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D013254:Steroid 17-alpha-Hydroxylase / Q000096:biosynthesis*; D016708:Synaptophysin / Q000032:analysis* / Q000096:biosynthesis
D019006:Neural Cell Adhesion Molecules; D012333:RNA, Messenger; D016708:Synaptophysin; C501892:CYP17A1 protein, human; D013254:Steroid 17-alpha-Hydroxylase