Distribution and Colocalization of Nitric Oxide Synthase and Calretinin in Myenteric Neurons of Developing, Aging, and Crohn's Disease Human Small Intestine

The pattern of distribution and colocalizationof nitric oxide synthase and the calcium-binding proteincalretinin in myenteric neurons and nerve fibers wereexamined in the human small intestine from preterm fetuses (14-17 weeks of gestation), normaladults (mean age 50 years old), old age (mean age 80years old), and Crohn's disease patients (mean age 30years old) using NADPH-diaphorase histochemistry and immunohistochemical techniques. In all agegroups investigated, NADPH-diaphorase-reactive andcalretinin-immunoreactive neurons and nerve fibers wereseen throughout the myenteric plexus. The highestproportion of NADPH-diaphorase-reactive neurons was foundin the myenteric ganglia of old age intestines (56% ofprotein gene product-immunoreactive neurons) followed byfetal intestines (41%) and Crohn's intestine (30%) compared with intestines of controladults (20%). A similar trend was observed forcalretinin-immunoreactive neurons where the highestproportion of immunoreactive neurons was found in themyenteric ganglia of old age intestines (28% of proteingene product-immunoreactive neurons), followed by fetalintestines (22%), and Crohn's intestines (18%) comparedwith intestines of control adults (9%). A colocalization of NADPH-diaphorase activity and calretininimmunoreactivity was only seen in the myenteric neuronsof fetal intestines (2% of NADPH-diaphorase-reactiveneurons were also calretinin-immunoreactive). The pattern of distribution of NADPH-reactive andcalretinin-immunoreactive neurons in the myentericganglia of fetal intestine differs from that of theother age groups. In the fetal intestine, the myenteric neurons containing either calretinin orNADPH-diaphorase are distributed through out themyenteric ganglia with no specific orientation to oneanother. In the intestines of control adult, Crohn's,and old age patients, single largecalretinin-immunoreactive neurons are surrounded by anumber of small NADPH-diaphorase-positive neurons, withthis feature being more prominent in intestines ofold-age and Crohn's disease patients. In summary, a high number ofboth NADPH-diaphorase-reactive andcalretinin-immunoreactive neurons were seen in themyenteric ganglia of fetal, old age, and Crohn'sintestines; we discuss that there may be a role for nitric oxide andcalretinin in the process of development, aging, andpathological changes in the human intestine associatedwith alteration in the calcium homeostasis in the myenteric neurons.