HMOX1 and autosomal dominant polycystic kidney disease: Figure 3 shows that the HO-1 protein level was significantly higher in tolvaptan-treated ADPKD patients compared to that in both untreated ADPKD patients and healthy subjects: 5.33 ± 3.34 vs. 2.08 ± 0.79 ng/mL, p = 0.012, vs. 1.97 ± 1.22 ng/mL, p = 0.012, respectively.