Intraperitoneal injection of sodium pyrophosphate was previously shown to reduce arterial calcification in an uremic mouse model . We used the dose of 160 micromole/Kg/day published by these authors and two weeks old Npt2a-/- pups for this experiment, because renal calcification is more pronounced when compared to older mice (Fig 4A and 4C). Size and body weight (BW) of mice in the treatment group were indistinguishable from vehicle and the animals appeared to be thriving well. Following sacrifice at four weeks of age we observed a reduction of renal mineral deposits by 33% in the treatment group (0.4±0.04, n = 9 vs. vehicle 0.7±0.06%, n = 12, p = 0.01) (Fig 4C and 4D) while mineralization size again was unaffected (Fig 4E). Plasma PPi levels at sacrifice were increased, albeit non-significantly (3.9±0.8, n = 9 vs. vehicle 2.0±0.4 micromole/l, n = 5, p = ns) (Fig 4F). Likewise, the U-PPi concentration was increased (244.9±33.2, n = 14 vs. vehicle 149.4 ± 28.8 micromole/l, n = 14, p = 0.039) (Fig 4G and panel B in S1 Fig).