[PO2-affinity of oxygen-sensitive intracellular signal cascades]

The oxygen partial pressure field in different organs ranging from 0 to 100 Torr is likely to be a mirror of oxygen sensitive intracellular signal cascades determining ion channel open probability, metabolic pathway activities and gene expression. High or low PO2 affinities of the particular signal cascade optimise the oxygen sensitive cellular response for adapting organ functions to variations of the oxygen supply conditions. The signal cascades are triggered by an oxygen sensor which is believed to be a heme protein. In some cases oxygen radicals are acting as second messengers revealing these signal cascades as an evolutionary highly conserved principle first described in bacteria.