title: Does motilin peptide regulate gastrointestinal motility of zebrafish? An in vitro study using isolated intestinal strips.
abstract: Motilin (MOT), a 22-amino-acid peptide hormone produced in the duodenal mucosa, stimulates gastrointestinal motility in mammals and birds, and it is a mediator of interdigestive motor complexes. Recently, expression of MOT-like peptide (MOTLP) and its receptor mRNAs was identified in zebrafish. The aim of the present study was to determine whether the zebrafish MOTLP (zfMOTLP, HIAFFSPKEMRELREKE) affects zebrafish gastrointestinal motility, with comparison to the effect of human MOT, in which five amino acids are identical to zfMOTLP at positions 5, 9, 15, 16, and 17. zfMOTLP caused small contractions of the rabbit duodenum and chicken ileum but, the sensitivity was about 3000-times lower than that of human MOT. zfMOTLP-induced contraction in the rabbit duodenum was decreased by pretreatment of the MOT receptor antagonist GM109, indicating that zfMOTLP could bind to the MOT receptor. zfMOTLP (3-100nM) increased the intracellular Ca2+concentration in zfMOT receptor-expressing HEK293 cells, but human MOT did not cause responses even at 100nM. In in vitro study using isolated zebrafish gastrointestinal strips, zfMOTLP caused only small contractions even at high doses (1-10μM). zfMOT receptor mRNA is detected in the gastrointestinal tract and brain to almost the same extent, and the expression level (40-70 copies/100ng total RNA) is much lower than that in the chicken gastrointestinal tract. These results suggest that the MOTLP/MOT receptor system is present in zebrafish, but its physiological role for regulation of gastrointestinal motility might be not significant due to the weak contractile activity and low expression level of the receptor.
authors.affiliation: School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan. Electronic address: tko-kita@rakuno.ac.jp.
authors.forename: Takio
authors.initials: T
authors.lastname: Kitazawa
authors.affiliation: School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
authors.forename: Maria
authors.initials: M
authors.lastname: Yoshida
authors.affiliation: School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Teraoka
authors.affiliation: Department of Biochemistry, National Cerebral and Cardiovascular Center Research Institute, Suita, Osaka 565-8565, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kaiya
mesh_terms: D000818:Animals; D002645:Chickens; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology*; D057809:HEK293 Cells; D006801:Humans; D066298:In Vitro Techniques; D007422:Intestines / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D009037:Motilin / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D010456:Peptides, Cyclic / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D011964:Receptors, Gastrointestinal Hormone / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D018013:Receptors, Neuropeptide / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D015027:Zebrafish / Q000378:metabolism
chemical_list: C093574:GM 109; D010456:Peptides, Cyclic; D012333:RNA, Messenger; D011964:Receptors, Gastrointestinal Hormone; D018013:Receptors, Neuropeptide; C050802:motilin receptor; D009037:Motilin
keywords: Distribution; Gastrointestinal motility; Motilin; Motilin receptor; Motilin-like peptide; Zebrafish