Direct observation of lactate and alanine by proton double quantum spectroscopy in rat hearts supplied with [3‐¹³C]pyruvate

Abstract

The °C-fractional enrichments in the lactate and alanine methyl carbon positions were determined by tH NMR spectroscopy of e~tracts of rat hearts t'~rfused with various coneentlations of [3-L'~C]pyruvate + unlabeled glucose or acetate, In general, the ~C-fraetional enrichment of the alaaine methyl carbon pool paralleled the t~C-fractional enrichment of the aeetyl.CoA which entered the TCA cycle (as determined by ~C-isotopomer analysis) while the t~C.fractional enrichment of the lactate methyl carbon was always significantly lower, consistent with a pool of lactate which does not mix with exogeneous [3-~'C]pyruvate, This has also been examined in intact, perfuscd, KCI-arrasted rat hearts supplied with [3-t'~C]pyravatc by proton doable quantum metabolite specific spectroscopy (MSS). A comparison of MSS spectra of intact hearts with one pulse spectra of extracts of those same hearts indicates there is a sizeable non-enriched pool of lactate in the intact hearts which is not visible by NMR spectroscopy.