Abstract
Summary
Weanling Wistar strain rats were allowed to age and everted intestinal sacs used to measure various parameters of valine transport at 4, 8, 12, 18, 24, and 40 weeks of age. The rats gained weight at the rate of 25 g/week until 18 weeks of age after which a weight gain of 9 and 4.5 g/week was observed at 24 and 40 weeks, respectively. The ratio of valine in the serosal medium to that in the mucosal medium remained relatively constant during the first 8 weeks after which it fell off precipitously and was only 1/6 its initial level at 40 weeks of age. Net transport of valine fell off in a linear manner between 4 and 18 weeks of age after which it remained at a relatively constant level. At the end of 40 weeks, net transport was 1/7 its initial value. The tissue uptake of valine was reduced 1/3 during the experimental period. The decrease in the transport parameters generally followed the increase in animal weight. The results show the necessity of standardizing the weight or age of the experimental animals used for intestinal transport studies.
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