title: Effects of ghrelin and motilin on smooth muscle contractility of the isolated gastrointestinal tract from the bullfrog and Japanese fire belly newt.
abstract: Ghrelin has been identified in some amphibians and is known to stimulate growth hormone release and food intake as seen in mammals. Ghrelin regulates gastrointestinal motility in mammals and birds. The aim of this study was to determine whether ghrelin affects gastrointestinal smooth muscle contractility in bullfrogs (anuran) and Japanese fire belly newts (urodelian) in vitro. Neither bullfrog ghrelin nor rat ghrelin affected longitudinal smooth muscle contractility of gastrointestinal strips from the bullfrog. Expression of growth hormone secretagogue receptor 1a (GHS-R1a) mRNA was confirmed in the bullfrog gastrointestinal tract, and the expression level in the gastric mucosa was lower than that in the intestinal mucosa. In contrast, some gastrointestinal peptides, including substance P, neurotensin and motilin, and the muscarinic receptor agonist carbachol showed marked contraction, indicating normality of the smooth muscle preparations. Similar results were obtained in another amphibian, the Japanese fire belly newt. Newt ghrelin and rat ghrelin did not cause any contraction in gastrointestinal longitudinal muscle, whereas substance P and carbachol were effective causing contraction. In conclusion, ghrelin does not affect contractility of the gastrointestinal smooth muscle in anuran and urodelian amphibians, similar to results for rainbow trout and goldfish (fish) but different from results for rats and chickens. The results suggest diversity of ghrelin actions on the gastrointestinal tract across animals. This study also showed for the first time that motilin induces gastrointestinal contraction in amphibians.
authors.affiliation: Dept. of Veterinary Science, 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: Dept. of Veterinary Science, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
authors.forename: Misato
authors.initials: M
authors.lastname: Shimazaki
authors.affiliation: Dept. of Veterinary Science, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Kikuta
authors.affiliation: Dept. of Veterinary Science, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Yaosaka
authors.affiliation: Dept. of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Teraoka
authors.affiliation: Dept. 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; D041981:Gastrointestinal Tract / Q000378:metabolism*; D054439:Ghrelin / Q000494:pharmacology*; D008297:Male; D009037:Motilin / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D011892:Rana catesbeiana; D054440:Receptors, Ghrelin / Q000378:metabolism*; D012455:Salamandridae
chemical_list: D054439:Ghrelin; D054440:Receptors, Ghrelin; D009037:Motilin
keywords: Bullfrog; Gastrointestinal motility; Ghrelin; Growth hormone secretagogue receptor 1a; Japanese fire belly newt; Motilin