TRPC4 and pulmonary arterial hypertension: After induction of PAH in Trpc4-knockout rats (Trpc4-KO) with a Sugen 5416 injection, followed by three weeks hypoxia exposure, histological grading in Trpc4 inactivated rats revealed a reduction in the density of severely occluded small pulmonary arteries and in the number of plexiform lesions.