Short-term hypoxia increases phosphorylated tyrosine hydroxylase at Ser31 and Ser40 in rat carotid body.

Long-term hypoxia (days to weeks) increases phosphorylation of tyrosine hydroxylase (TH) at Ser31 and Ser40 in the carotid body (CB). In the present study, we examined the time course of TH phosphorylation at Ser31 and Ser40 in CB of rats exposed to short-term hypoxia (within 1 day) for 0-24 h. Using immunoblotting, the signal intensities of both phosphorylated TH were more intense in CB of rats exposed to hypoxia for 6, 12, 18, and 24h than those of controls. Using immunohistochemistry, immunoreactive intensities of both phosphorylated TH were significantly more intense in glomus cells after rats were exposed to hypoxia for 6, 12, 18, and 24 h than those of controls (p<0.05). These results show that phosphorylation of TH at Ser31 and Ser40 is increased in CB glomus cells by short-term hypoxia, suggesting that activation of TH via phosphorylation contributes to the facilitation of catecholamine biosynthesis in CB glomus cells at an early stage of hypoxia.