Oxygen is an essential gasotransmitter directly sensed via protein gasoreceptors

The current restrictive criteria for gasotransmitters exclude oxygen (O 2 ) as a gasotransmitter in vertebrates. In this manuscript, I propose a revision of gasotransmitter criteria to include O 2 per se as a signaling molecule and 'essential gasotransmitter' for vertebrates. This revision would enable us to search for protein‐based O 2 ‐binding sensors (gasoreceptors) in all cells in the brain or other tissues rather than specialized tissues such as the carotid body or gills. If microorganisms have protein‐based O 2 ‐binding sensors or gasoreceptors such as DosP or FixL or FNR with diverse signaling domains, then eukaryotic cells must also have O 2 ‐binding sensors or gasoreceptors. Just as there are protein‐based receptor(s) for nitric oxide (GUCY1A, GUCY1B, CLOCK, NR1D2) in cells of diverse tissues, it is reasonable to consider that there are protein‐based receptors for O 2 in cells of diverse tissues as well. In mammals, O 2 must be acting as a gasotransmitter or gaseous signaling molecule via protein‐based gasoreceptors such as androglobin that very likely mediate acute sensing of O 2 . Accepting O 2 as an essential gasotransmitter will enable us to search for gasoreceptors not only for O 2 but also for other nonessential gasotransmitters such as hydrogen sulfide, ammonia, methane, and ethylene. It will also allow us to investigate the role of environment‐derived metal ions in acute gas (or solute) sensing within and between organisms. Finally, accepting O 2 per se as a signaling molecule acting via gasoreceptors will open up the field of gasocrinology.