FT-IR microspectroscopic detection of metabolically deuterated compounds in the rat cerebellum: a novel approach for the study of brain metabolism.
Deuteration provides a novel means for studying metabolism in biological organisms and avoids the use of radioisotopes. Ingestion of D2O enriched drinking water causes deuterium to be metabolically incorporated into molecules within tissues. The incorporation of deuterium into various chemical functional groups then can be monitored via infrared spectroscopy. The excellent spatial resolution that can be achieved with Fourier transform infrared (FT-IR) microspectrometers allows collection of infrared spectra from select microscopic regions of tissue specimens. Thus, combining deuteration together with FT-IR microspectroscopy enables analysis of metabolic activities by probing subregions within the microscopic field. In the present study, adult rats were given drinking water containing 30% or 40% D2O for 5 1/2 weeks. Frozen sections were prepared from the cerebellum, and infrared spectra were collected from the molecular layer, granule cell layer and white matter with FT-IR microspectrometers, using both conventional and synchrotron sources. The CD:CH and ND,OD:NH,OH ratios were highest in the molecular layer and lowest in the white matter. The high ratios in the molecular layer are consistent with the active synthesis and recycling at synapses, which are abundant structures in this layer. The low levels in the white matter are consistent with radioactive measures that found slow turnovers of proteins and lipids in myelin, which is the main constituent of white matter. In addition to describing the metabolic incorporation of deuterium, a graphic description of the distribution of chemical functional groups in the various layers of the cerebellum is presented. In summary, this study demonstrates that FT-IR microspectroscopy in conjunction with administration of D2O in drinking water can be used to reveal relative metabolic activities in various layers of the cerebellum. We predict that metabolic activities in other tissues and tissues in different states, e.g., disease states, can be analyzed in a similar manner.
Wetzel
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DL
Microbeam Molecular Spectroscopy Laboratory, Kansas State University, Manhattan 66506, USA.
Slatkin
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DN
LeVine
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SM
D000818:Animals; D002531:Cerebellum / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology; D003903:Deuterium; D051381:Rats; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
D003903:Deuterium