Studies of Protein Metabolism in Intestinal Epithelial Cells*

Lipkin, Martin; Quastler, Henry

doi:10.1172/jci104520

Cited by 37 publications

(15 citation statements)

References 12 publications

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“…The t 1/2 of radioactive amino acids incorporated into protein of the whole mucosa or into crypt cells of 32-day-old rats is similar to published values for the adult mouse in which the disappearance of label from the crypts is caused by emigration of cells [15].…”

Section: Discussionsupporting

confidence: 84%

“…Prolonged administration of steroids to adult mice, a species that also has a n intestinal growth spurt a t weaning [19], does not significantly alter cell kinetics in the jejunum [15]. These data suggest that the effects of steroids on the adult intestine may be maximal, or that steroids exert action during a critical period in development.…”

Section: Discussionmentioning

confidence: 73%

“…T h e rate of cell turnover is similar in the intestines of 21-and 32-dayold rats, but the rate of protein turnover in either crpyt cells or in whole mucosa is more rapid in the 2 1-day-old rat (two times as rapid in crypt cells and one and onehalf times as rapid in whole mucosa, as indicated by the half-lives of amino acids in intestinal proteins). Thus, in the young rat, the rate of protein turnover in intestinal mucosa cannot be correlated with cell turnover as it can be in the adult [15].…”

Section: Discussionmentioning

confidence: 96%

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Postnatal Development of the Small Intestine of the Rat: Changes in Mucosal Morphology at Weaning

1969

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ExtractAt 15 days after birth, the small intestine of the rat showed a striking increase in relative weight, an increased depth of intestinal crypts, a n elevation of the mitotic and the labeling index of crypt cells, and a decrease in the ratio of height of the villi to depth of the crypts.Metabolically, the biological half-life of 14C phenylalanine incorporated into protein was decreased in the intestine of 21-day-old rats compared with that of the 32-day-old rat. With autoradiography, a decreased half-life of 3H-leucine in crypt cells was noted in rats 5 and 21 days of age, compared with fully weaned rats 32 days of age. These observations indicated that protein turnover is not completely dependent on cellular turnover in suckling rats.Artificial feeding of suckling rats from 9 to 15 days of age produced an increase in the relative weight, mitotic index, depth of crypts, and activity of invertase in the jejunum. Prolonged administration of hydrocortisone to newborn rats resulted in similar changes in the duodenum and in the jejunum, but not in the ileum. These changes could be related to a n increased rate of cellular migration along the villi of the duodenum and the jejunum. I t was concluded that both diet and hormones were important factors in the marked changes in intestinal cell proliferation and differentiation observed a t weaning. SpeculationT h e usual changes in cellular proliferation and differentiation of the intestinal mucosa of the weanling rat and the observation that these changes can be stimulated precociously suggest that the intestinal tract of suckling rats could be used to investigate further those factors important to the control of cell differentiation. Since cell turnover increases to adult levels after 15 days of age, the observed increase in protein turnover in suckling and in weanling rats, compared with that of adult rats, suggests that a t these ages protein turnover is not coordinated with cell turnover.Introduction markable morphological and chemical changes. The rate of migration of epithelial cells along the villus Cellular proliferation has been studied extensively in in the suLking rat is only one-fourth to one-fifth that of animals and in man, usually in the adult [4,14, 161. the adult animal, but increases during weaning to rates When the rat is weaned, the intestine undergoes re-observed in the adult intestine [12]. Concomitantly,

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Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 73%

Section: Discussionmentioning

confidence: 96%

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Postnatal Development of the Small Intestine of the Rat: Changes in Mucosal Morphology at Weaning

1969

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“…The small intestinal mucosa resists atrophy during protein deprivation for a longer time than many other tissues (1)(2)(3). Recent studies have shown that the jejunal mucosa is even more resistant than the ileal mucosa (4,5).…”

Section: Introductionmentioning

confidence: 99%

“…The epithelium of the intestinal mucosa has a rapid turnover rate, which is reduced during protein deficiency (6) and starvation (7), but nevertheless this tissue synthesizes a large amount of protein each day (8,9). It is probably because of the rapid rate of growth that the small intestinal mucosa of the proteindeficient animal incorporates parenterally administered radioactive amino acids into protein more efficiently than other tissues (3,8,10,11).…”

Section: Introductionmentioning

confidence: 99%

Protein starvation and the small intestine

Hirschfield¹,

Kern²

1969

J. Clin. Invest.

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A B ST RA CT Weanling rats were fed diets which contained either no protein or 27% protein. In one experiment after 23-35 days both groups were given l-leucine-4,5-3H either intragastrically or intraperitoneally and then sacrificed 24 hr later. In a second experiment animals were given these diets for 21 days and sacrificed 3, 6, or 12 hr after either intragastric or intraperitoneal administration of the labeled leucine. In both experiments the intestinal mucosa of proximal and distal segments of the small intestine was scraped, weighed, the protein concentration measured, and the specific activty of the mucosal protein was determined.The wet weight of the mucosa and the protein concentration of the mucosa were significantly greater in the control animals than in the protein-depleted animals. The mucosal protein per 100 g of body weight was the same in the protein-deprived and the control groups. The specific activity of the intestinal mucosal protein was higer in the protein-deprived animals than in the control animals.In the protein-deprived animals the proximal segment incorporated more radioactive amino acid into mucosal protein than did the distal segment at 3, 6, 12, and 24 hr after the amino acid was given by mouth. A similar difference was found between the proximal and distal segments of the control animals 6 hr after oral adminisstration of l-leucine-'H. On the other hand, when the l-leucine-3H was given intraperitoneally to both groups

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Morphological effects of a large single dose of cycloheximide on the intestinal epithelium of the rat

Altmann

1975

Am. J. Anat.

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Adult male rats received 15 mg/kg cycloheximide and the subsequent morphological effects at three and six hours after injection were evaluated using histometry, light and electron microscopy, histological demonstration of terminal web and acid phosphatase, and radioautography with tritiated thymidine. Rapid atrophy of the villi took place, progressing from the villus tip by premature exfoliation of epithelial cells. The crypts also diminished by random exfoliation of many crypt cells and by partial or complete disintegration. Mitosis and epithelial cell migration were absent. By six hours, the area occupied by the villi and the crypts per unit length of histological section was decreased by about 70-90% in most of the small intestine but only by about 40-60% in the duodenum and the terminal ileum. In the upper half of the villi, the epithelium was strongly positive for acid phosphatase and contained large numbers of round bodies resembling primary lysosomes. In the lower half, the microvillous border and terminal web were found to be disrupted. Animals receiving only 5 mg/kg cycloheximide also showed the atrophy of villi and crypts, and the round bodies resembling lysosomes. Evidence from several sources has indicated that protein synthesis in normal villus epithelial cells subsides toward the villus tip and becomes minimal at exfoliation. At exfoliation, proteins responsible for epithelial cohesion probably fail because they are no longer replenished. Cycloheximide appears to accelerate this process.

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Studies of Protein Metabolism in Intestinal Epithelial Cells*

Cited by 37 publications

References 12 publications

Postnatal Development of the Small Intestine of the Rat: Changes in Mucosal Morphology at Weaning

Postnatal Development of the Small Intestine of the Rat: Changes in Mucosal Morphology at Weaning

Protein starvation and the small intestine

Morphological effects of a large single dose of cycloheximide on the intestinal epithelium of the rat

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