Glucagon infusion alters the hyperpolarized 13C‐urea renal hemodynamic signature

Renal urea handling is central to the urine concentrating mechanism, and as such the ability to image urea transport in the kidney is an important potential imaging biomarker for renal functional assessment. Glucagon levels associated with changes in dietary protein intake have been shown to influence renal urea handling; however, the exact mechanism has still to be fully understood. Here we investigate renal function and osmolite distribution using [13C,15N] urea dynamics and 23Na distribution before and 60 min after glucagon infusion in six female rats. Glucagon infusion increased the renal [13C,15N] urea mean transit time by 14%, while no change was seen in the sodium distribution, glomerular filtration rate or oxygen consumption. This change is related to the well‐known effect of increased urea excretion associated with glucagon infusion, independent of renal functional effects. This study demonstrates for the first time that hyperpolarized 13C‐urea enables monitoring of renal urinary excretion effects in vivo. Hyperpolarized 13C urea MRI during 60 min infusion of glucagon resulted in an increased 13C‐urea renal mean transit time for urea, without changing GFR, renal blood flow or renal oxygen tension. This change is related to the well‐known effect of increased urea excreation associated with the glucagon infusion, independent of renal functional effects. This study demonstrate that hyperpolarized 13C‐urea enables monitoring of renal urinary excretion effects in vivo.