title: Gastric and pyloric sphincter muscle function and the developmental-dependent regulation of gastric content emptying in the rat.
abstract: Feeding intolerance is a common issue in the care of preterm neonates. The condition manifests as delayed emptying of gastric contents and represents a therapeutic challenge, since the factors accounting for its manifestations are unknown. The main goal of this study was to comparatively investigate the age-related function of rat gastric and pyloric smooth muscle and their putative regulators. We hypothesized that a reduced gastric muscle contraction potential early in life contributes to the delayed gastric emptying of the newborn. Newborn and adult rat gastric (fundus) and pyloric sphincter tissues were comparatively studied in vitro. Shortening of the tissue-specific dissociated smooth muscle cell was evaluated, and expression of the key regulatory proteins Rho-associated kinase 2 and myosin light chain kinase was determined. Gastric and pyloric smooth muscle cell shortening was significantly greater in the adult than the respective newborn counterpart. Expression of myosin light chain kinase and Rho-associated kinase 2 was developmentally regulated and increased with age. Pyloric sphincter muscle expresses a higher neuronal nitric oxide synthase and phosphorylated vasodilator-stimulated phosphoprotein content in newborn than adult tissue. Compared with later in life, the newborn rat gastropyloric muscle has a Ca(2+)-related reduced potential for contraction and the pyloric sphincter relaxation-dependent modulators are overexpressed. To the extent that these rodent data can be extrapolated to humans, the delayed gastric emptying in the newborn reflects reduced stomach muscle contraction potential, as opposed to increased pyloric sphincter tone.
authors.affiliation: Physiology and Experimental Medicine Program, Hospital for Sick Children Research Institute, University of Toronto, Toronto, Ontario, Canada; and.
authors.forename: Curtis
authors.initials: C
authors.lastname: Sobchak
authors.affiliation: Physiology and Experimental Medicine Program, Hospital for Sick Children Research Institute, University of Toronto, Toronto, Ontario, Canada; and.
authors.forename: A Felipe
authors.initials: AF
authors.lastname: Fajardo
authors.affiliation: Physiology and Experimental Medicine Program, Hospital for Sick Children Research Institute, University of Toronto, Toronto, Ontario, Canada; and.
authors.forename: Yulia
authors.initials: Y
authors.lastname: Shifrin
authors.affiliation: Physiology and Experimental Medicine Program, Hospital for Sick Children Research Institute, University of Toronto, Toronto, Ontario, Canada; and.
authors.forename: Jingyi
authors.initials: J
authors.lastname: Pan
authors.affiliation: Physiology and Experimental Medicine Program, Hospital for Sick Children Research Institute, University of Toronto, Toronto, Ontario, Canada; and Department of Paediatrics and Physiology, University of Toronto, Toronto, Ontario, Canada jaques.belik@sickkids.ca.
authors.forename: Jaques
authors.identifier: 0000-0003-1470-7827
authors.initials: J
authors.lastname: Belik
mesh_terms: D000818:Animals; D005746:Gastric Emptying; D005748:Gastric Fundus / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D018994:Myosin Light Chains / Q000235:genetics / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000235:genetics / Q000378:metabolism; D011708:Pylorus / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D054460:rho-Associated Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D018994:Myosin Light Chains; D052248:Nitric Oxide Synthase Type I; D054460:rho-Associated Kinases
keywords: feeding intolerance; newborn; smooth muscle; stomach