PDE6H and idiopathic pulmonary fibrosis: In contrast, PDE6D subunit was significantly down-regulated in the IPF lungs as compared to the donor lungs (relative mRNA expression: 2.44 ± 0.28 and 0.30 ± 0.56, respectively) and PDE6H showed a tendency of down-regulation in the IPF lungs as compared to the donor lungs (relative mRNA expression: -7.22 ± 0.34 and -8.98 ± 0.66, respectively).