Male and female C57BL/6 mice were obtained from Charles River Laboratory, MA. Male and female Npt2a-/- mice (B6.129S2-Slc34a1tm1Hten/J, Stock No: 004802), and Enpp1asj/asj mice (C57BL/6J-Enpp1asj/GrsrJ, Stock No: 012810) were purchased from The Jackson Laboratory, ME. The Enpp1asj allele is partially active and shows approximately 15% level of Enpp1 activity compared to wild-type controls . Mice were genotyped by PCR amplification of genomic DNA extracted from tail clippings as described [29, 38–40]. Mice were weaned at 3 weeks of age and allowed free access to water and regular chow (1.0% calcium, 0.7% phosphorus, of which 0.3% phosphorus is readily available for absorption, Harlan Teklad TD.2018S). Mice received daily intraperitoneal (i.p.) injection of Hanks Buffered Saline (Gibco, Life Sciences) or sodium pyrophosphate in HBSS for two weeks until age four weeks as previously described (160 micromole/Kg/day) according to . To determine whether renal mineral deposits persist beyond weaning age mice were followed for an additional 10 weeks of age after weaning on regular chow. The background of all mouse lines is C57Bl6, use of littermates for controls further reduced bias based on genetic background. No difference in renal mineral deposits was observed between sexes as previously reported by us [12, 36] and thus genders were combined here.