Korean J Gastroenterol.
2002 Jan;39(1):4-12.
Mechanisms of Motilin Action on Smooth Muscle of the Human Stomach
- Affiliations
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- 1Department of Internal Medicine, Masan Samsumg Hospital, Masan, Korea. jchrhee@smc.samsung.co.kr
- 2Department of Internal Medicine, Samsung Medical Center and Samsung Cheil Hospital, Seoul, Korea.
- 3Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea.
- 4Department of Internal Medicine, Gyeongsang National University College of Medicine, Chinju, Korea.
Abstract
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Background/Aims: Motilin is an intestinal peptide that stimulates the contraction of gut smooth muscle. A discrepancy exists between the in vivo (neurally mediated) and in vitro (direct action on a smooth muscle receptor) mechanisms of motilin action in many species. We investigated in vitro mechanisms of motilin action on human gastric smooth muscle.
Methods
Antral cirular muscle strips of the surgical tissue obtained during gastrectomy, were used to measure contractile force and electrical activity. Dispersed muscle cells were used to measure L-type Ca2+ current and electrical activity.
Results
Motilin of 1-100 nM contracted smooth muscle in a concentration-dependent manner. Motilin-induced contractions were unaffected by tetrodotoxin or atropine treatment. Nifedipine or Ca2+-free bath solution blocked motilin (10 nM)-induced contractions. Low concentration of motilin (1 nM) resulted in an increase in acetylcholine (0.1~100 M)-induced contractions. By patch clamp recording technique, motilin (1 or 10 nM) did not modify the L-type Ca2+ current, but motilin-induced membrane depolarization was detected. Erythromycin also contracted smooth muscle with membrane depolarization but verapamil inhibited the contraction.
Conclusions
These results suggest that motilin contracts smooth muscle through a direct action on smooth muscle receptor and Ca2+ influx through the L-type Ca2+ channel, which is due to membrane depolarization, also mediates motilin-induced contractions.
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