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 biologic al organisms and avoids the use of radioisotopes. Ingestion of D2O enr iched drinking water causes deuterium to be metabolically incorporated into molecules within tissues. The incorporation of deuterium into va rious chemical functional groups then can be monitored via infrared sp ectroscopy. The excellent spatial resolution that can be achieved with Fourier transform infrared (FT-IR) microspectrometers allows collecti on of infrared spectra from select microscopic regions of tissue speci mens. Thus, combining deuteration together with FT-IR microspectroscop y enables analysis of metabolic activities by probing subregions withi n the microscopic field. In the present study, adult rats were given d rinking water containing 30% or 40% D2O for 5 1/2 weeks. Frozen sectio ns were prepared from the cerebellum, and infrared spectra were collec ted from the molecular layer, granule cell layer and white matter with FT-IR microspectrometers, using both conventional and synchrotron sou rces. The CD:CH and ND,OD:NH,OH ratios were highest in the molecular l ayer and lowest in the white matter The high ratios in the molecular l ayer are consistent with the active synthesis and recycling at synapse s, 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 constitu ent of white matter. In addition to describing the metabolic incorpora tion of deuterium, a graphic description of the distribution of chemic al functional groups in the various layers of the cerebellum is presen ted. In summary, this study demonstrates that FT-IR microspectroscopy in conjunction with administration of D2O in drinking water can be use d to reveal relative metabolic activities in various layers of the cer ebellum. We predict that metabolic activities in other tissues and tis sues in different states, e.g., disease stales, can be analyzed in a s imilar manner.