Also, separate evaluation of interstitial and luminal mineralization and PPi levels and/or activity of PPi generating enzymes may be of interest in future studies. Finally, determining how urinary pH, anion gap, citrate, oxalate, magnesium, and the expression of uromodulin (Tamm-Horsfall protein, THP) or Opn  modify PPi action may help better understanding the pathogenesis of renal mineralization in Npt2a-/- mice.