HMOX1 and cyclic hematopoiesis: In MCT-PH and CH-PH rats, simvastatin administration led to significantly higher levels of HO-1 protein expression, of 310 ± 40% (MS group, p < 0.05 versus M group, Figure 4A) and 420 ± 130% (HS group, p < 0.05 versus H group, Figure 4B).