Physiological And Metabolic Magnetic Resonance Studies

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NMR methods provide a unique approach for the investigation of metabolic and physiological processes in intact systems, perfused organs, cell suspensions, as well as by examination of cell extracts. This project investigates how chemical toxins or physical factors alter metabolic processes, with primary emphasis on perfused mouse heart preparations. Studies have focused on intracellular ions, but other cellular metabolites are also evaluated. It has been shown previously that under conditions in which hearts are stressed prior to an ischemic insult, females exhibit greater protection from ischemia/reperfusion injury compared with males (Cross H, Murphy E, Steenbergen C. Ca2+ loading and adrenergic stimulation reveal male/female differences in susceptibility to ischemia-reperfusion injury. Am. J. Physiol. 2002;283:H481-H489). Recent studies using transgenic mice with different expression of the alpha or beta estrogen receptor demonstrated that the beta estrogen receptor was responsible for the protection from ischemia/reperfusion injury seen in the female hearts. A second area of research has focused on determining the mechanisms by which borate exerts physiological and toxicological effects. We previously demonstrated that the combination of borate and serine inhibits the enzyme gamma-glutamyl transpeptidase via the formation of a ternary complex, and demonstrated that a boronate analog of this complex, L-2-amino-4-borono butanoic acid, inhibits this enzyme with much greater potency than a 1:1 serine-borate mixture. This result suggests the possibility of a general involvement of ternary complexes as the basis for the physiological and toxicological effects of borate. We have recently characterized the structures of other ternary complexes formed from borate, alcohols, and trypsin, using both NMR spectroscopy and X-ray crystallography. In addition to the fundamental insight into borate biochemistry and toxicology that these studies provide, they suggest approaches for the development of boronate-based effectors of biological function.