ENDOTHELIN-1 EXPRESSION IN MYENTERIC NEURONS CULTURED FROM RAT SMALL-INTESTINE

Endothelin is a potent vasoactive peptide. More recently, endothelin-1 (ET-1) has been found in neural tissues such as spinal cord, brain an d peripheral ganglion cells. Inagaki (Gastroenterology 101 (1991) 47) reported evidence of ET-1-like immunoreactivity in enteric neurons, bu t there are no reports of ET-1 peptide or mRNA expression specifically in myenteric neurons. Using a primary culture of myenteric neurons, w e set out to evaluate ET-1 peptide and mRNA expression. Myenteric neur ons were cultured using a dissection and enzyme dispersion technique. ET-1 reactivity was localized to neurons and ET-1 levels from cells an d media were assayed by radioimmunoassay under a variety of media cond itions or with depolarizing buffer or veratridine (75 mu M). Prepro ET -1 mRNA expression was determined by Northern analysis of total RNA ut ilizing a rat ET-1 cDNA. ET-1 immunoreactivity was observed almost exc lusively in myenteric neurons. Cells contained 0.78 pg/mu g protein an d did not vary with variations in media conditions. Basal release/secr etion into media occurred but was not enhanced by depolarizing media o r veratridine. High levels of ET-1 mRNA expression were identified. Th ese results of high level constitutive expression of ET-1 linked with previous reports of ET-1 modulation of cholinergic intestinal smooth m uscle contraction suggest a neuromodulatory role.