Influence of injected pyruvate concentration on metabolism using hyperpolarized C

Introduction: Metabolic imaging with hyperpolarized [1-C]pyruvate enables the real-time in-vivo observation of metabolism [1]. The typical injected pyruvate dose is a multiple of physiological concentration levels, which may lead to saturation effects in pyruvate metabolism. Under this condition the observed conversion rates between pyruvate and its metabolic products are not only dependent on metabolic activity but also on the injected pyruvate dose. The aim of this study is to investigate the influence of injected pyruvate dose on its cellular uptake and enzymatic conversion in the heart, liver, and kidney of rats. This dose-response study estimates in the healthy rat the lowest dose of pyruvate that gives good metabolite SNR in various organs. Reducing the amount of injected pyruvate is also beneficial for advanced acquisition schemes to avoid a very large difference between signals from pyruvate and its metabolic products. Furthermore, preventing saturation of metabolite concentrations can simplify metabolic modeling.