Aminopeptidase, lactase and sucrase activities have been followed during 5 days
in the jejunum and in the ileum of starved adult rats. Enzyme activities have been determined
in the mucosal homogenates as well as in the purified brush border membranes and expressed
as activities per intestinal length (segmental activities) or as activities per milligram of protein
(specific activities).
The segmental and specific activity of aminopeptidase was increased in the ileum during
the first 2 days of starvation, suggesting that aminopeptidase may have during the first days of
starvation a conservative role by preventing an important loss of tissue protein.
In all conditions, lactase activity was strikingly enhanced by starvation whereas sucrase
activity showed no changes or decreased activity. Lactase stimulation was initiated during the
first 24 h of starvation reaching its maximum after 2 days. The various experimental conditions
leading to a specific or to a nonspecific stimulation of intestinal lactase activity have
been discussed.
Previous work in our laboratory and in others suggest that protein malnutrition plays an important role in the pathogenesis of hepatic dysfunction after jejunoileal bypass for morbid obesity. This experimental study was undertaken to attempt to correlate hepatic dysfunction (the criterion used was the bromsulphalein clearance) to morphological and enzymatic adaptation of the functioning intestine in the rat. It was observed that the period of impaired bromsulphalein clearance is concomitant with a slight ileal morphological adaptation and especially with a period of selective adaptation of maltase and sucrase activities, whereas there is no increase in aminopeptidase activity. These data support the hypothesis that after jejunoileal bypass a preferential absorption of carbohydrates along with a protein deficiency state could occur and as in kwashiorkor it results in an impaired nutritional status, a major contributing factor to bypass-induced liver injury.
Intralipid was given to adult rats for 4 days either by intragastric or intravenous infusion. The villus height, protein content and the levels of sucrase, lactase and aminopeptidase activities were determined in the jejunum. The results were compared to values found in control rats fed orally with an equilibrated isocaloric diet. Intragastric or intravenous infusion of Intralipid caused (a) a 50% reduction in the protein content of the brush border membrane, (b) a significant drop of the specific (expressed per milligram protein) and segmental (expressed per centimeter intestinal length) activities of the disaccharidases, (c) the maintenance of aminopeptidase activity and (d) the lengthening of the villi in the jejunum. The major loss in disaccharidase activities was obtained when fat was given intravenously. Arguments favoring a hormone-mediated effect of the infused lipids on the intestinal function are presented and discussed.
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