XDH and cystic kidney disease: However, RENF mice had extensive apoptosis of tubular cells (Figure 3F), and elevated plasma calcium and ALP (Table 1), consistent with tertiary hyperparathyroidism, as well as elevated plasma creatinine concentrations, which were not reported in the Xor−/− mice [13], whereas Xor−/− mice had renal cysts (Table 3), which were not detected in RENF mice.