CYBB and cyclic hematopoiesis: While increases in gp91phox were reported in the MCT rat model [27,33], other studies found no change in gp91phox expression in mice exposed to CH [32], chronic intermittent hypoxia (CIH) [36], or MCT [37], rats exposed to MCT [26], or the Fawn-Hooded rat [27], a model that spontaneously develops PH.