Carbon Monoxide, Oxygen, and Pseudohypoxia

Numerous studies have shed light on the intricate biological roles that carbon monoxide (CO) and oxygen (O 2 ) play under various physiological and pathophysiological conditions, both independently and interdependently. This chapter discusses the interplay between CO and O 2 from a comparative physiological standpoint and discusses how their signaling pathways impact one another to modulate specific cellular and physiological responses. The varying effects of CO on vasomotor tone depend on various factors, including how CO is generated (endogenously or exogenously), how much CO is present in the bloodstream (anemic hypoxia or pseudohypoxia), and from which isoform of HO it is generated (HO-1 or HO-2). CO and hypoxia are thought to act independently of each other through different signaling pathways, activating HO-1 and HIF-1, respectively.