Development of the Functions of the Small Intestine in Mammals and Man

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1 Development of the Functions of the Small Intestine in Mammals and Man Ο. KOLDOVSKY Laboratory of Developmental Nutrition Institute of Physiology of the Czechoslovak Academy of Sciences Praha Krc With 70 figures and 11 tables BASEL (Switzerland) S. KARGER NEW YORK

2 S. Karger AG, Arnold-Böcklin-Strasse 25, CH-4000 Basel 11 (Switzerland) All rights, including that of translation into other languages, reserved. Photomechanic reproduction (photocopy, microcopy) of this book or parts thereof without special permission of the publishers is prohibited. Copyright 1969 by S. Karger AG, Basel Printed in Switzerland by Effingerhof, Brugg

3 CONTENTS Acknowledgements Introduction VII VIII A. Changes in the Morphological Structure of the Small Intestine of Mammals During Development 1 a) Macrostructure of the Small Intestine 1 Colour 1 The Length and Weight of the Small Intestine 2 The Width of the Small Intestine 3 b) Microstructure of the Small Intestine 4 α) Developmental Changes of Typical Structures of the Small Intestine 5 Villi 5 Crypts 7 Muscularis Mucosae 8 Lymphatic Tissue 8 ß) The Structure of the Developing Intestinal Epithelial Cell 9 Size 9 Microvilli 10 Nuclei of Enterocytes 10 Mitochondria 12 Other Structures 12 Vacuolar Structures 13 Paneth Cells 15 c) The Rate of Cell Exchange in the Small Intestine 16 d) Effect of Various Factors on Structural Changes During Development 18 B. The Development of Motor Activity of the Digestive Tract 20 a) Swallowing 20 b) Automatic (Rhytmic) Movements 20 c) Movement Along the Digestive Tract 21 C. Development of Absorption of Water, Ions and Vitamins 23 a) Absorption of Water from the Small Intestine 23 b) Absorption of Ions 23 c) Vitamin Absorption 24

4 IV D. Digestion and Absorption of Carbohydrates 25 a) Digestion of Polysaccharides 25 b) Digestion of Disaccharides 27 Changes of ß-Galactosidase Activities in the Small Intestine During the Postnatal Development 29 Ad. 1. The Existence of Several ß-Galactosidase Activities 30 Ad. 2. ThePossible Significance of Different ß-Galactosidases for Lactose Absorption 42 Ad. 3. Postnatal Changes 44 α) Rats 45 ß) Mice 45 γ) Rabbits 46 ) Guinea-pigs 47 Ad. 4. Regulation of Galactosidase Activity in the Jejunum and Ileum of Infant Rats During Postnatal Development with Remarks on Invertase 55 α) The Effect of Changes in the Amount of Lactose in the Diet 56 ß) The Effect of Adrenalectomy on the Decrease in ß-galactosidase Activity 59 c) The Absorption of Glycides 63 α) Absorption of Disaccharides 67 ß) Absorption of Monosaccharides Prenatal Development of Monosaccharide Absorption Postnatal Development of Monosaccharide Absorption 68 E. The Digestion and Absorption of Lipids 75 a) Digestion of Fats 75 b) Absorption of Lipids During Development 84 c) The Fate of Fat in the Small Intestinal Wall 86 α) Fat Distribution in the Wall of the Small Intestine 87 ß) Esterification of Labelled Fatty Acids in the Small Intestine 92 γ) Phospholipoid Formation 93 d) The Transport Phase 95 F. Development of Absorption of Proteins and Aminoacids 96 a) Protein Absorption 96 α) The Existence and Duration of Protein Transfer 96 ß) Characteristics of the Intestinal Tract Conditioning the Transfer of Proteins Across its Wall Protein Breakdown During Development 97 Protein Breakdown in the Stomach 98 Proteolytic Activity in the Pancreas 101 Proteolytic Activity in the Small Intestine 101 Peptidase Activities in the Small Intestine 103

2. Characteristics of the Mechanism of Transfer of Proteins in the Intestinal Tract 105 Evidence for Pecularities of the Small Intestine of Infant Animals for Protein Transfer in Intact Infant

5 2. Characteristics of the Mechanism of Transfer of Proteins in the Intestinal Tract 105 Evidence for Pecularities of the Small Intestine of Infant Animals for Protein Transfer in Intact Infant Animals 106 Histological Studies of Protein Absorption 111 Protein Transport From the Small Intestine of Suckling Mammals 112 The Significance of Absorption of Other Protein Molecules 113 γ) Factors Affecting the Duration of Transfer of Intact Proteins in Different Animal Species After Birth The Effect of Hormones The Effect of Diet 117 b) Absorption of Amino-acids 119 V G. Developmental Changes in Some Other Enzymatic Activities 121 a) Alkaline Phosphatase 121 Changes in Total Alkaline Phosphatase Activity in the Duodenum 121 Alkaline Phosphatase Activity in Different Parts of the Small Intestine 122 Localisation of Alkaline Phosphatase in Enterocytes 124 Differences in Alkaline Phosphtitases During Development 128 b) Metabolism of Glucurcnqdes in the Small Intestine During the Development 134 Beta-glucurondase Activity 134 c) Other Enzymes 138 H. Functional Development of the Small Intestine of Human Fetuses 139 a) Anatomy and Histology 139 The Length of the Small Intestine 139 Colour 141 Structure of the Small Intestinal Wall 141 Microscopic Studies of Enterocytes 144 b) Development of Enzymes with Unspecified Functions 145 α) Nonspecific Esterase 145 ß) Alkaline Phosphatase 148 Alkaline Phosphatase Activity During Embryonal Development of the Small Intestine as Determined Biochemically 148 Acid Phosphatase 150 γ) Beta-glucurondase 150 Beta-glucurondase Activity in the Mucosa of the Large Intestine in Infants 150 c) Motility of the Digestive Tract 152 d) Digestion and Absorption of Fats 153 Prenatal Development 153 Postnatal Development 153 e) Digestion and Absorption of Proteins Development of Structure of the Stomach Development of Gastric Proteolytic Activity Secretion of Gastric Juice Development of Pancreatic Enzymes Proteolytic and Peptidase Activities in the Small Intestine 160

6 ντ 6. Absorption of Aminoacids in the Small Intestine of Human Fetuses Absorption of Proteins 164 f) Digestion and Absorption of Glycides 165 ci) Prenatal Development Digestion Absorption 168 β) Postnatal Development 176 I. Conclusions 178 References 179

7 VII ACKNOWLEDGEMENTS This monography summarizes the work of several years. The results were obtained in cooperation with different co-workers. I am glad that I can convey here my thanks to DoΒτπΙoνń, FALTOVA, HAηx, HERΙx- GOVÁ, HIR~OVA, ΗοζκονÁ, CHYTIL, Jmmsον&, KRAML, ΚjνλνκονΑ, KUBÁT, Μλsνz oνλ, Μuzυcaxκονλ, PELICHOVA, ΡRΟCΗ ΖΚA, Rοκos and UHER (Prague) and to Asr (Lund), Doµixns (Warsaw), FRIEDRICH (Berlin), KRETCHMER (Palo Alto), LEVIN (Sheffield), NoACk (Berlin), SCHENK (Berlin), Sτxsmmxz (Palo Alto), TIMOFEEvA, UGOLEV, YEzUIrOVA (Leningrad) and others.

8 VIII INTRODUCTION Many functions change during postnatal development, when also food composition changes [cf. Ηλ ν and Κοmονsκf, 1967]. Here we shall deal with change in the small intestine during development. The small intestine is the site where most nutritients and other substances enter the body after birth. The human fetus, available in this country, was also studied and a special chapter is devoted to it. This study could help indirectly to clarify some problems such as the causes of the observed developmental changes. Some of them could be related to changes in food composition, others to endocrine regulation. Finally the differences between the jejunum and ileum attracted our special attention. Relations between those two parts of the small intestine change during development in all species was examined.

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