Deficiency of Phenylethanolamine N-Methyltransferase in Norepinephrine-Producing Pheochromocytoma |
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Authors: | Kimura Noriko Togo Akira Sugimoto Takako Nata Koji Okamoto Hiroshi Nagatsu Ikuko Nagura Hiroshi |
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Institution: | (1) Department of Biochemistry, Tohoku University School of Medicine, Sendai;(2) Department of Anatomy, School of Medicine, Fujita Health University, Toyoake, Japan;(3) Department of Pathology, Tohoku University School of Medicine, 2-1, Seiryo-machi Aoba-ku, 980-77 Sendai, Japan |
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Abstract: | Pheochromocytoma is a catecholamine (CA)-producing tumor that is classified into two types: the norepinephrine (NE) and the
mixed NE and epinephrine type (E-type) from plasma CA levels. Phenylethanolamine N-methyltransferase (PNMT) is the terminal
enzyme in CA synthesis; it catalyzes the synthesis of E from NE. It is not known whether the absence of immunoreactive PNMT
is paralleled by a lack of PNMT mRNA. The mRNA of tyrosine hydroxylase (TH) and PNMT in seven pheochromocytomas, five NE-type
and two E-type tumors, were examined by Northern blot analysis andin situ hybridization (ISH) technique. TH mRNA was detected in all tumors but PNMT mRNA was limited only to the E-type tumors. In
addition to our previous immunohistochemical study of 70 pheochromocytomas and paragangliomas in which all pheochromocytomas
had cells immunoreactive to TH, but PNMT was expressed only in E-type, we concluded that NE-type pheochromocytoma lacks PNMT
both at the mRNA and protein levels, resulting in an inability to produce E. The essential difference between NE-type and
E-type pheochromocytoma is that the NE-type lacks PNMT. |
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Keywords: | phenylethanolamine N-methyltransferase (PNMT) epinephrine (E) norepinephrine (NE) pheochromocytoma Northern blot hybridization in situ hybridization (ISH) |
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