Abstract
We have previously reported studies indicating that gastric mucin (hog) is relatively resistant to enzymatic hydrolysis in vitro. 1 However, indirect evidence suggests more complete digestion in the gastrointestinal tract. 1 To further investigate the digestion of mucin we have fed purified gastric mucin as the source of nitrogen, to a series of albino rats, and from nitrogen analyses of the urine and feces determined its degree of digestibility in vivo.
Our experimental procedures differed little from those commonly employed in the determination of utilization, digestibility and biological value of proteins. Young growing albino rats weighing 40–60 gm. were placed in cages so designed that urine and feces could be collected separately. Nitrogen intake was calculated from the weight of food consumed. The small amount spilled was corrected for by determining its nitrogen content and subtracting from the calculated food nitrogen. All nitrogen analyses were by the Kjeldahl method.
The purified mucin 2 used in the preparation of the mucin diet gave the following analyses: Nitrogen 7.50%. Reduction after acid hydrolysis (Shaffer-Hartmann) 35.4% (as glucose) and ash 2.51%. The diet was designed to be complete for the rat exclusive of its protein content. This necessitated the addition of a small amount of yeast concentrate (Yeast Vitamin-Harris), the amount added being sufficiently small to be disregarded for practical purposes. 3 A preliminary period on a diet similar except for the absence of mucin was employed in order to determine the fecal nitrogen on a nitrogen-free diet, or the so-called metabolic nitrogen. Four-day periods were allowed between changes in diets to insure the attainment of equilibrium. Collection periods were each of one week's duration. The compositions of the diets were as follows:
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