Structural and functional organization of the brush border of intestinal epithelial cells

Eichholz, Alexander

doi:10.1016/0005-2736(67)90037-5

Cited by 208 publications

(15 citation statements)

References 19 publications

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“…' Finally, the cell membrane fraction, morphologically the least satisfactory of our preparations, has the usual type of plasmalemmal enzyme activities and little else . In contrast to the situation in other tissues (7,25,33,34,36,37) it has no alkaline p-nitrophenylphosphatase activity, and its NADH-cytochrome c reductase, as well as part of the Mgt+-ATPase activity could be accounted for by mitochondrial contamination as indicated by experiments and calculations similar to those described in the case of zymogen granule membranes . ' Smooth microsomes, zymogen granule membranes, and plasmalemmal fractions have a rather similar lipid composition characterized by high sphingomyelin and cholesterol content (2) .…”

Section: Discussionmentioning

confidence: 71%

“…5'-nucleotidase (5, 9, 20-23, 25, 33-35), ß-leucyl naphthylamidase (22,25,33,36,37), and Mgt+-ATPase (5,20,22,(34)(35)(36)(37)(38) (Table II), are also highly concentrated in the pancreatic plasmalemmal fraction . In addition, they are present in different concentrations in smooth microsomes and zymogen granule membranes .…”

Section: Enzyme Activities In Pancreatic Cell Fractionsmentioning

confidence: 99%

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Composition of Cellular Membranes in the Pancreas of the Guinea Pig

Meldolesi

Jamieson

Palade

1971

The Journal of Cell Biology

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A comparative study of the enzymic activities of membrane fractions derived from guinea pig pancreatic homogenates has yielded the following results: Rough microsomal membranes (derived from the rough ER) have the reductase activities of the two microsomal electron transport systems but lack enzyme activities of Golgi-type (TPPase) and plasmalemmal-type (5'-nucleotidase, ß-leucyl naphthylamidase, Mg-ATPase). Smooth microsomal membranes (derived primarily from the Golgi complex), zymogen granule membranes, and plasmalemmal fractions possess overlapping enzyme activities of plasmalemmal type, in different relative concentrations for each fraction. In addition, the smooth microsomal membranes exhibit TPPase and ADPase activity and share with rough microsomes the reductase activities of the two electron transport chains. Taken together with recent data on the lipid composition of the same fractions (2), these results indicate that the membranes of the pancreatic exocrine cell are chemically and functionally distinct, and hence do not mix with one another during the transport of secretory products.

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Section: Discussionmentioning

confidence: 71%

Section: Enzyme Activities In Pancreatic Cell Fractionsmentioning

confidence: 99%

Composition of Cellular Membranes in the Pancreas of the Guinea Pig

Meldolesi

Jamieson

Palade

1971

The Journal of Cell Biology

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“…With few exceptions which could be ascribed to heavy microsomal contamination (52), sphingomyelin has been found in high concentration in plasmalemmal fractions isolated from liver homogenates (51, 53-58) (range from 14% [55] to 33% [56] of total phospholipids) and erythrocytes (59,60) . The same applies for cholesterol which is found in high concentrations in cell membrane fractions prepared from liver (51-58, 61, 62), intestinal brush borders (61,63,64), erythrocytes, 9 (59, 61), kidney (62), urinary bladder (65), and HeLa cells (66) .…”

Section: Washing Of Pancreatic Membranes With Albuminmentioning

confidence: 82%

Composition of Cellular Membranes in the Pancreas of the Guinea Pig

Meldolesi

Jamieson

Palade

1971

The Journal of Cell Biology

141

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1 3 0The lipid composition of rough and smooth microsomal membranes, zymogen granule membranes, and a plasmalemmal fraction from the guinea pig pancreatic exocrine cell has been determined . As a group, membranes of the smooth variety (i .e ., smooth microsomes, zymogen granule membranes, and the plasmalemma) were similar in their content of phospholipids, cholesterol and neutral lipids, and in the ratio of total lipids to membrane proteins . In contrast, rough microsomal membranes contained much less sphingomyelin and cholesterol and possessed a smaller lipid/protein ratio . All membrane fractions were unusually high in their content of lysolecithin (up to _~20% of the total phospholipids) and of neutral lipids, especially fatty acids . The lysolecithin content was shown to be due to the hydrolysis of membrane lecithin by pancreatic lipase ; the fatty acids, liberated by the action of lipase on endogenous triglyceride stores, are apparently scavenged by the membranes from the suspending media . Similar artifactually high levels of lysolecithin and fatty acids were noted in hepatic microsomes incubated with pancreatic postmicrosomal supernatant . E 600, an inhibitor of lipase, largely prevented the appearance of lysolecithin and fatty acids in pancreatic microsomes and in liver microsomes treated with pancreatic supernatant .In the first article of this series, we have described the separation of membrane subfractions from rough microsome-, smooth microsome-, and zymogen granule fractions isolated from homogenates of guinea pig pancreas . We have also shown that a cell membrane fraction can be obtained from the same source (1) .These fractions represent membrane-bounded compartments which are involved in the synthesis, segregation, intracellular transport, and discharge of secretory proteins . In an attempt to understand how the membranes of these compartments interact with one another during the secretory process, we have investigated their chemical composition and enzyme activities . In this paper the lipid composition of the membranes is described .At the onset of this study, we anticipated that a small fraction of the digestive enzymes stored in the gland, particularly in zymogen granules and in the duct system, could be released during tissue homogenization and fractionation and thereupon cause artifactual degradation and alteration of membrane components . In this respect, it has been reported that pancreatic lipase is active in the cold (2) and that at least some proteases may become activated during cell fractionation (3) . Indeed, our studies showed that released lipolytic enzymes extensively affect the lipid composition of the isolated membranes . These alterations have been evaluated and the data on membrane lipids have been corrected accordingly .

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“…Pregnant Swiss ICR mice were injected i.p. with 0.5 ~tg of epidermal growth factor (EGF) per g b.wt at 15,16 and 17 days of gestation and fetuses were removed at 18 days of gestation. EGF treatment had no effect on the weight of the fetuses and on the length of the small intestine.…”

mentioning

confidence: 99%

Epidermal growth factor (EGF) accelerates the maturation of fetal mouse intestinal mucosa in utero

1982

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Summary. Pregnant Swiss ICR mice were injected i.p. with 0.5 ~tg of epidermal growth factor (EGF) per g b.wt at 15,16 and 17 days of gestation and fetuses were removed at 18 days of gestation. EGF treatment had no effect on the weight of the fetuses and on the length of the small intestine. No modification of the protein and DNA contents was noted. However brush border alkaline phosphatase and trehalase activities were significantly increased as well as endoplasmic reticulum membrane-bound glucose-6-phosphatase.Epidermal growth factor (EGF) is a small polypeptide mitogen that has been isolated from the male mouse submaxillary gland 2 and from human urine 3. The presence of EGF in human Brunner's gland, shown by Elder et al. 4, suggests that EGF may have a role in mucosal growth and control of gastrointestinal secretion. In the adult male mouse Scheving et al. 5'6 have demonstrated that EGF rapidly stimulates DNA synthesis in some regions of the digestive tract. In the newborn mouse EGF stimulates ornithine decarboxylase activity in the stomach and duodenum 7 and accelerates the maturation of the intestinal mucosa 8. Using an organ culture method of fetal mouse small intestine, we have observed that EGF induces the differentiation of the rough endoplasmic reticulum in absorptive cells after 72 h of culture 9. The aim of this work was to determine the effect of EGF on the fetal mouse small intestine in utero by measuring the protein and DNA contents as well as enzymatic activities of the brush border and endoplasmic reticulum. Results were comparable with both products. Fetuses were removed at 18 days of gestation. The entire small intestine of the fetuses was removed, measured and cut into 3 equal parts. For each assay, the intestinal thirds of 5 fetuses were pooled, weighed and homogenized in 49 vol. of ice-cold red• water in an Omnimixer during 2 min at full speed. The homogenates were used immediately for enzymatic determinations. Protein was measured by the method of Lowry et al. l~ with bovine serum albumine as standard and DNA content was determined by the method of Burton" as modified by Giles Results and discussion. The effects of daily injections of EGF for 3 days beginning at 15 days of gestation have been studied in the small intestine of fetuses at 18 days of gestation. As shown in table 1 the weight of the EGFtreated fetuses, the length of their small intestine and the weight of the different intestinal segments are comparable to that of the controls. Furthermore no modification of the protein and DNA contents is noted along the small intestine. The development of some brush border membrane hydrolytic activities has been investigated. Significant increases of alkaline phosphatase and trehalase activities are recorded along the entire length of the small intestine following EGF treatment (table 2), except for trehalase activity in the distal thirds where the increase is nonsignificant. It is interesting to note that even though alkaline phosphatase and trehalase activities increase following EGF treatm...

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Structural and functional organization of the brush border of intestinal epithelial cells

Cited by 208 publications

References 19 publications

Composition of Cellular Membranes in the Pancreas of the Guinea Pig

Composition of Cellular Membranes in the Pancreas of the Guinea Pig

Composition of Cellular Membranes in the Pancreas of the Guinea Pig

Epidermal growth factor (EGF) accelerates the maturation of fetal mouse intestinal mucosa in utero

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