UBC Theses and Dissertations
Certain studies on the digestive enzyme systems (sucrase, maltase and lactase) of the small intestine of the Wistar rat Bose, Robert John
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 immediately 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 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 adaptive response to substrates could be demonstrated for either sucrase or maltase.
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