Distribution of κ‐Opioid Receptor in the Pulmonary Artery and its Changes During Hypoxia

Abstract

The present study evaluated the distribution of kappa-opioid receptors (kappa-ORs) in pulmonary arteries (PAs) in rats and investigated whether kappa-ORs are altered in PAs during hypoxia. An animal model of hypobaric/hypoxic pulmonary hypertension and a pulmonary artery smooth muscle cell (PASMC) model of hypoxia were utilized. Distribution of kappa-ORs was determined by fluorescence immunohistochemistry and changes in kappa-ORs expression in PAs and PASMCs were determined by fluorescence immunohistochemistry or Western blot techniques. The kappa-ORs were primarily distributed in the smooth muscle layer of the PAs and in the nucleus of PASMCs. The expression of the kappa-ORs were increased in PAs of rats subjected to hypoxia for 1-4 week (P < 0.01). Accordingly, the expression of kappa-ORs in PASMCs were also increased when subjected to hypoxia for 12-36 hr (P < 0.05). The present study has provided evidence for the first time of the precise location of kappa-ORs in PAs and PASMCs of rats and that hypoxia upregulates expression of kappa-ORs.