Figure 2.

Potential interaction of heme oxygenase-2- (HO-2-) generated CO with cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS) in glomus cells of the carotid body. (a) Under normoxia, HO-2-generated CO is relatively high, resulting in inhibition of both CSE and CBS activity. H₂S production is relatively low, contributing to low sensory activity in glomus cells. (b) Under hypoxia, CO generation from HO-2 is reduced, resulting in removal of CO inhibition on CSE and CBS activity. H₂S levels are increased due to enhanced CSE and CBS activities. Increased H₂S may activate Ca²⁺ channels due to membrane depolarization via the inhibition of K⁺ channels, which in turn excites sensory responses in glomus cells.