Stimulation of duodenal muscle contraction by porcine or canine motilin in the dog in vivo.
Motilin is a 22 amino acid polypeptide stimulating intestinal muscle contraction. Structure analysis of motilin purified from hog and from dog intestinal mucosa reveals different amino acids in positions 7, 8, 12, 13, and 14. Previous in vitro experiments suggested this species-related structural heterogeneity could generate different bioactive characteristics for these two peptides. This study was designed to compare the stimulatory mechanism of canine and porcine motilins on dog duodenal motility in vivo, testing the hypothesis that canine motilin stimulates a receptor located on the intestinal muscle, while porcine motilin is acting on intrinsic nerves regulating intestinal muscle contraction. Synthetic porcine and canine motilins were administered through a catheter inserted in the caudal pancreatic duodenal artery to stimulate the contraction of a close irrigated duodenal segment. In acute experiments performed on anaesthetized animals, both peptides induced a similar motor stimulation that was inhibited by tetrodotoxin and atropine. In experiments in conscious animals, canine and porcine motilins were equally potent in inducing premature phase III of the migrating motor complex, and the action of both peptides was abolished by atropine or hexamethonium. This study reveals that the structural heterogeneity between porcine and canine motilin does not influence the bioactivity of both peptides in the dog in vivo and suggests that circulating endogenous motilin stimulates intestinal muscle contraction through intrinsic excitatory nerves.
Poitras
P
P
Centre de recherche clinique André-Viallet, Hôpital Saint-Luc, Université de Montréal, Quebec.
Trudel
L
L
Lahaie
R G
RG
St-Pierre
S
S
D000758:Anesthesia; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001626:Bethanechol Compounds / Q000494:pharmacology; D004285:Dogs; D004386:Duodenum / Q000502:physiology*; D006584:Hexamethonium Compounds / Q000494:pharmacology; D007269:Injections, Intra-Arterial; D009037:Motilin / Q000008:administration & dosage / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects*; D013268:Stimulation, Chemical; D013552:Swine; D013779:Tetrodotoxin / Q000494:pharmacology
D001626:Bethanechol Compounds; D006584:Hexamethonium Compounds; D013779:Tetrodotoxin; D009037:Motilin; D001285:Atropine