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Phenylethanolamine N-methyl transferase expression in mouse thymus and spleen
Michelle D Warthan1, Jessica G Freeman, Kathryn E Loesser
1Department of Biology, Virginia Commonwealth University, Richmond, Virginia 23284, USA.
Brain, Behavior, and Immunity
|July 5, 2002
Summary
This study found high levels of epinephrine-producing enzyme (PNMT) in young mouse thymus, comparable to the brainstem. These findings suggest thymus cells can synthesize epinephrine.
Area of Science:
- Immunology
- Neuroendocrinology
- Biochemistry
Background:
- Catecholamines, like epinephrine, are typically found in mammalian neurons and chromaffin cells.
- The thymus, a primary lymphoid organ, is crucial for T-cell development.
Purpose of the Study:
- To investigate the presence and activity of phenylethanolamine N-methyl transferase (PNMT), the epinephrine-synthesizing enzyme, within the thymus.
- To determine the localization and levels of PNMT and its mRNA in the thymus and compare them to other tissues.
Main Methods:
- Measurement of PNMT enzyme activity in thymus and spleen tissue.
- Administration of a PNMT inhibitor (LY134046) to assess its effect on thymus PNMT activity.
- In situ hybridization to localize PNMT mRNA within the thymus and spleen.
Main Results:
- Surprisingly high levels of PNMT activity were detected in the thymus of young mice, comparable to brainstem levels.
- PNMT mRNA was found throughout the thymus, with higher concentrations in the cortex compared to the medulla.
- PNMT activity was minimal in the spleen, with only a few PNMT mRNA-expressing cells observed.
Conclusions:
- Cells within the thymus of young mice possess the enzymatic machinery to synthesize epinephrine.
- This discovery suggests a potential novel role for catecholamine synthesis within the thymus, impacting immune function or development.