Haem oxygenase in enteric nervous system of human stomach and jejunum and co-localization with nitric oxide synthase

Recent evidence suggests that carbon monoxide (CO) may be a neurotransmitte r, similar to nitric oxide (NO) in the enteric nervous system. The distribu tion of haem oxygenase (HO), the biosynthetic enzyme for CO, has been deter mined in the enteric nervous system of animals, but little is known about t he distribution of HO in human gastrointestinal tract. The present study in vestigated the expression of HO and its colocalization with NO synthase (NO S), the biosynthetic enzyme for NO, in human antrum and jejunum. HO isoform s were identified using immunohistochemistry and NOS was identified by immu nohistochemistry or NADPH-d histochemistry. HO-2 immunoreactive (IR) cell b odies in enteric ganglia and nerve fibres in longitudinal and circular musc le were found in both antrum and jejunum. Go-localization of HO-2 and NOS w as about 40% in HO-2 containing cell bodies of myenteric ganglia and only 1 0% or less in cell bodies of submucous ganglia. HO-1 immunoreactivity was n ot detected in antrum or jejunum. The results suggest that CO is produced i n human enteric ganglion neurones and indicate a possible role of CO as a n eurotransmitter and possible interaction between HO and NOS pathways in inh ibitory neurotransmission in the human gastrointestinal tract.