Effect of Rapid Changes in 13C Pyruvate Concentration on Lactate and Alanine Pool Sizes and 13C Enrichment in the Heart

Karlos X. Moreno¹, Scott Sabelhaus¹, Matthew E. Merritt¹, A Dean Sherry¹, Craig R. Malloy¹

Pyruvate binds to albumin. In the absence of albumin, the metabolic products of 2 mM hyperpolarized-[1-13C1]-pyruvate (HP-Pyr) are easily detected in the isolated heart but much higher [pyruvate] is required in the presence of albumin. The T1 of [1-13C1]-pyruvate is significantly reduced in the presence of albumin containing fatty acids and even more prominent in the presence of fatty acid-free albumin. Albumin catalyzes the relatively slow exchange of pyruvate methyl protons with solvent protons, suggesting transient covalent binding to albumin. The kinetics of these complex pyruvate/albumin interactions may play a significant role in hyperpolarized 13C imaging in vivo.