This core measures serum, serum ultrafiltrate, and urine chemistries and calculates urine supersaturations (SS) for human (Projects by Coe and Lingeman) and pig {Project by Evan) protocols, as well as performing assays of serum oxalate (Project core1). The core also performs assays to measure upper limit of metastability with respect to calcium oxalate and calcium phosphate in urine (Projects by Coe and Lingeman). The core measures iothalamate in serum and urine for calculation of iothalamate clearances (Project by Coe). Calculation of euglycemic-hyperinsulinemic glucose clamp induced glucose utilization will be done (Project by Coe) in collaboration with the Diabetes Research and Training Center. Peripheral blood monocyte vitamin D receptor levels (PBM VDR) will be determined in patients studied in the proposed GCRC protocols (Project by Coe). Assays of protein abundance (by Western blot)will be carried out for VDR, calcium receptor (CaR), calbindin 9 and calbindin 28 in renal cortical biopsy specimens obtained from Project by Lingeman;mRNA expression levels will be measured for VDR and CaR.