Document Detail

Immunohistochemical localization of monoamine oxidase type B in pancreatic islets of the rat.
MedLine Citation:
PMID:  15923360     Owner:  NLM     Status:  MEDLINE    
Monoamine oxidase (MAO) is regarded as a mitochondrial enzyme. This enzyme localizes on the outer membrane of mitochondria. There are two kinds of MAO isozymes, MAO type A (MAOA) and type B (MAOB). Previous studies have shown that MAOB activity is found in the pancreatic islets. This activity in the islets is increased by the fasting-induced decrease of plasma glucose level. Islet B cells contain monoamines in their secretory granules. These monoamines inhibit the secretion of insulin from the B cells. MAOB is active in degrading monoamines. Therefore, MAOB may influence the insulin-secretory process by regulating the stores of monoamines in the B cells. However, it has not been determined whether MAOB is localized on B cells or other cell types of the islets. In the present study, we used both double-labeling immunofluorescence histochemical and electron microscopic immunohistochemical methods to examine the subcellular localization of MAOB in rat pancreatic islets. MAOB was found in the mitochondrial outer membranes of glucagon-secreting cells (A cells), insulin-secreting cells (B cells), and some pancreatic polypeptide (PP)-secreting cells (PP cells), but no MAOB was found in somatostatin-secreting cells (D cells), nor in certain other PP cells. There were two kinds of mitochondria in pancreatic islet B cells: one contains MAOB on their outer membranes, but a substantial proportion of them lack this enzyme. Our findings indicate that pancreatic islet B cells contain MAOB on their mitochondrial outer membranes, and this enzyme may be involved in the regulation of monoamine levels and insulin secretion in the B cells.
Yu-Hong Huang; Akio Ito; Ryohachi Arai
Publication Detail:
Type:  Journal Article     Date:  2005-05-27
Journal Detail:
Title:  The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society     Volume:  53     ISSN:  0022-1554     ISO Abbreviation:  J. Histochem. Cytochem.     Publication Date:  2005 Sep 
Date Detail:
Created Date:  2005-09-13     Completed Date:  2005-10-18     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9815334     Medline TA:  J Histochem Cytochem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1149-58     Citation Subset:  IM    
Department of Anatomy, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan.
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MeSH Terms
Fluorescent Antibody Technique
Islets of Langerhans / cytology,  enzymology*,  ultrastructure
Microscopy, Electron
Monoamine Oxidase / metabolism*
Rats, Sprague-Dawley
Subcellular Fractions / enzymology
Reg. No./Substance:
EC Oxidase

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