Organoid Culture of Bovine Coronary Arteries Reverses the Response to Hypoxia from Relaxation to Contraction Associated with Alterations in Mechanisms Controlling Protein Kinase G

We provided evidence that bovine coronary arteries (BCA) relax to hypoxia (PO2 ~10 torr) by oxidizing cytosolic NADPH and that hypoxia contracts pulmonary arteries by removing a peroxide/protein kinase G (PKG)‐mediated relaxation. Hypoxia‐elicited relaxation of 20mM KCl contracted BCA caused increased thiol oxidation‐dimerization of PKG and increased PKG activity (VASP phosphorylation). BCA were organoid cultured for 48 hours in the absence (48h Control) and presence of 10μM ODQ to deplete soluble guanylate cyclase (by ~75%, chronic ODQ). Contraction to hypoxia was observed in 48h organoid cultured BCA, associated with decreased dimerization of PKG. Chronic ODQ treatment enhanced KCl contraction (vs. 48h Control BCA) and attenuated contraction to hypoxia and relaxation to an NO donor. While acute treatments with 10μM ODQ and 0.1mM ebselen (a peroxide & peroxynitrite scavenger) did not alter BCA relaxation to hypoxia, these agents attenuated the contraction to hypoxia in organoid cultured BCA. The data suggest that organoid culture changes the mechanisms regulating PKG in a manner which seems to participate in converting the response to hypoxia from relaxation to contraction.