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Sucrase, Maltase and Lactase Activity in the Small Intestine of the Laboratory Wistar Rat, Raised on a Basal Diet

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Sucrase, Maltase and Lactase Activity in the Small Intestine of the Laboratory Wistar Rat, Raised on a Basal Diet CERTAIN STUDIES ON THE DIGESTIVE ENZYME SYSTEMS (SUCRASE, MALTASE AND LACTASE) OF THE SMALL INTESTINE OP THE WISTAR RAT by ROBERT JOHN BOSE B.S.A., The University of British Columbia, 1955 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OP SCIENCE IN AGRICULTURE iii the division of Animal Science We accept this thesis as conforming to the required standard Members of the Division THE UNIVERSITY OF BRITISH COLUMBIA October,1957. ii - II. ABSTRACT The primary objective of this study was to establish the nature and extent of the changes with age in sucrase, maltase and lactase activity in the small intestine of the laboratory Wistar rat, raised on a basal diet. The author was, in addition, interested in the possibility of these changes being brought about by the presence or absence of certain specific dietary factors. Analysis have shown marked changes in the activities of these three enzymes with advancing age in Wistar rats weaned at 21 days on to a basal diet. Lactase activity was found to remain at a high level from 18 to 20 days during which time a sharp and uniform drop in activity was indicated. The extent of this drop was found to be great, approximately 80 per cent of the pre-weaned level. In contrast sucrase activity of the small intestine in the pre-weaned rat was negligible and underwent a sharp increase in activity at the weaning age of 21 days. Maltase activity in the pre-weaned Wistar rat was appreciable and was found to increase significantly at weaning. Early weaning at 15 days brought about an earlier decline in lactase activity and a corresponding early rise in sucrase and maltase activities. When early weaning was immedi• ately followed by the feeding of condensed milk no apparent maintenance of lactase activity was noted. Similarily when older rats, 28 days of age, were fed condensed milk no increase - iii - in lactase activity was apparent. Neither the condensed milk nor basal diets induced apparent differences on the effect of early weaning on sucrase and maltase activity. Apparent maintenance of lactase activity above those levels demonstrated in rats weaned at 21 days on to a basal diet was accomplished by fostering 16 day old rats on dams which had littered from four to five days prior to this transfer and which were assumed to be lactating at a somewhat greater rate than had the original mothers. It was noted however that this fostering process had no apparent influence on the extent of the changes in sucrase and maltase activities. The feeding of purified sugar diets containing two different levels of each of the three sugars, sucrose, maltose and lactose, had little effect on any of the three carbohydrases studied. Growth rates of the rats on these purified diets showed marked differences. The author suggests that the maintenance of lactase activity might be associated with the presence of an inductive component present in the milk of the freshly lactating dam, a component not necessarily present in the milk of the later period of lactation, and not necessarily a component of processed cow's milk. The absence of an adaptive lactase response to the feeding of lactose in this study and those of other workers suggest that lactose itself is unlikely this inducer. No adap• tive response to substrates could be demonstrated for either sucrase or maltase. In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Hea'el\of my Department or by his representative. It is understood that copying or publication of this thesis for// financial gain shall not be allowed without my written permission. ROBERT JOHN BOSE Department of THE nTVTRTnw on- awTMar. ^r.rjmr.v, The University of British Columbia, Vancouver 8, Canada. Date .TTTT.V jc\ 1957 I. ACKNOWLEDGEMENT The writer wishes to thank Dean Blythe Eagles, Chairman of the Division of Animal Science, for providing the facilities with which to conduct this experiment. Sincere appreciation is expressed to Dr. W. D. Kitts, Assistant Professor of Animal Husbandry, for sug• gesting this problem and for his direction, assistance and criticism during the course of this study. Thanks are expressed to Dr. A. J. Wood and to Dr. J. J. R. Campbell for their advice and criticisms. TABLE OP CONTENTS PAGE I. ACKNOWLEDGEMENT i II. ABSTRACT ii III. INTRODUCTION 1 IV. HISTORICAL 3 A. Sucrase 3 B. Maltase 5 C. Lactase 7 D. General 8 V. METHODS AND MATERIALS 15 A. Methods 15 1. Housing of the Experimental Animals.. 15 2. Sacrifice and Dissection of the Animals..... 15 3. The Storage of Tissue Samples 16 4. Preparation of the Tissue Homogenates 16 5. Moisture Determination 17 6. Nitrogen Determination 17 7. The Determination of Enzyme Activity 18 B. Materials 23 1. The Basal Diet 23 2. The Condensed Milk Diet 24 3. The Synthetic Diets .. 25 4. Copper Solution 26 5. Perric Sulfate Solution (According to Bertrand) 26 6. Potassium Permanganate Solution 26 7. Sugar Solutions 26 8. Buffer Solutions 27 VI. RESULTS AND DISCUSSION 28 A. Optima pH for Sucrase, Maltase and Lactase Activity 28 B. The H-ion Concentration of the Small Intestine of the Rat at Various Ages 31 C. The Relationship Between Homogenate Nitrogen Content and Enzyme Activity 34 TABLE OF CONTENTS (Continued) PAGE D. The Effect of Inanition on Sucrase, Maltase and Lactase Activity 37 E. Sucrase, Maltase and Lactase Activity From Birth to 72 Days of Age. in the Small Intestine of the Wistar Eat Weaned on to a Basal Diet at 21 Days 39 F. The Effect on Sucrase, Maltase and .. Lactase Activity of Early Weaning and the Feeding of Condensed Milk and a Basal Diet at Various Ages in the Laboratory Wistar Rat 49 G. The Effect on Sucrase, Maltase and Lactase Activity of the Small Intestine of the Young Wistar Rat of Prolonged Suckling on Foster Dams 57 H. The Effect on Sucrase, Maltase and Lactase Activity of Various Levels of the Three Sugars, Sucrose, Maltose and Lactose in a Purified Synthetic Diet .for the Laboratory Wistar Rat. VII. SUMMARY AND CONCLUSIONS 71 VIII. BIBLIOGRAPHY 74 Ill. INTRODUCTION Digestion in its broad sense refers to the mechanical and chemical degradation of complex dietary constituents to forms that are suitably prepared for the absorptive processes of the alimentary tract. The rate at which any animal "breaks down" its complex dietary is necessarily a function of many mechanical and chemical processes. The composition of a mammal's dietary changes markedly from birth to adult life. The young ingests almost exclusively its mother's milk, the mature or post weaned animal utilizes essentially none of this food for its dietary needs. In view of the many highly specific digestive mechanisms, it seems reasonable to conclude that accomodation for this changing dietary must necessarily be made for by associated changes in the digestive complex of the animal. A great number of investigators have described the numerous enzymes or ferments present in the various regions of the alimentary tract. Much work has been conducted regarding the digestibility of various dietary constituents for a wide group of species. There is however, only scanty information on the quantitative measurement of the digestive enzymes. In this investigation the three carbohydrases, sucrase ( <*-D-glucosidoinvertase), maltase ( oC-D-glucopyranosidase) and lactase (y3 -D-galactosidase) have been assayed quantitatively in the small intestine of the Wistar rat at various ages. In addition, experiments have been conducted to demonstrate the presence or absence of enzymatic adaptation to dietary changes in these three carbohydrases present in this digestive organ of the laboratory rat. The Wistar rat was employed in this experiment because of its rapid growth rate, genetic uniformity, low cost and its availability in large numbers. The practical applications arising from information regarding the nature of the changes in the digestive complex of the laboratory rat would be the extrapolation of these fundamental principles to the feeding of domestic animals such as the pig, sheep and ox. Inherent changes in the elaboration of lactase would necessitate the feeding of lactose at definite ages in a manner paralleling the production of this hydrolytic enzyme in the digestive tract. If the elaboration of digestive enzymes is largely controlled by the presence of their specific substrates in the ingesta the feeding of starch, for example, to young dairy calves could substitute for the more costly milk diet commonly fed these animals. IV. HISTORICAL A brief description of the three carbohydrases is felt appropriate as an introduction to the discussion of the literature. A. Sucrase; Sucrase has been known the longest of all the carbo• hydrases. In 1828 Dumas and Boullay (14) described the uptake of water during the fermentation of sucrose by yeast. Sucrase has been termed invertase, invertin and saccharase. Two types of invertase are described, a fructosidase attacking the fructose end, and a glucosidase attacking: the glucose end of the sucrose molecule (44). Both types are found in certain yeasts. The invertebrates and vertebrates possess the glucoinvertase exclusively. Sucrase is reported absent from the saliva and gastric secretions of mammals (31,7)• Its presence in the small intestine of the foetus and still-born has been reported by Keene et al (27) and Tachibana (45). Neuberg and Mandl (44) suggest that the elaboration of intestinal sucrase is inde• pendent on the presence of food in the intestinal tract.
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