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Studies on the phospholipases of rat intestinal mucosa.

ABSTRACT: 1. Subcellular distribution and characteristics of different phospholipases of rat intestinal mucosa were studied. 2. The presence of free fatty acid was necessary for the maximal hydrolysis of lecithin (phosphatidylcholine), but there was no accumulation of lysolecithin (1 or 2-acylglycerophosphorylcholine);lysolecithin accumulated when the reaction was carried out in the presence of sodium deoxycholate and at or above pH8.0. 3. The fatty acid-activated phospholipase B as well as lysolecithinase showed optimum activity at pH6.5, whereas for the phospholipase A it was about pH8.6. 4. The bulk of the phospholipase A was present in the microsomal fraction, whereas the phospholipase B and lysolecithinase activities were distributed between the microsomal and soluble fractions of the mucosal homogenate. 5. Phospholipase A was equally distributed between the brush border and brush-border-free particulate fraction, with the brush border having highest specific activity, whereas the other two activities were distributed between the brush-border-free particulate and soluble fractions. 6. Various treatments showed marked differences between the phospholipase A and phospholipase B activities, but not between phospholipase B and lysolecithinase activities. 7. By using (beta[1-(14)C]-oleoyl) lecithin it was shown that the mucosal phospholipase A was specific for the beta-ester linkage of the lecithin molecule.

SUBMITTER: Subbaiah PV

PROVIDER: S-EPMC1179108 | biostudies-other | 1970 Jun

REPOSITORIES: biostudies-other

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Project description:ImportanceThe normal absorptive function and structural maintenance of the intestinal mucosa depend on a constant process of proliferation of enterocytic stem cells followed by progressive differentiation toward a mature phenotype. The mechanisms that govern enterocytic differentiation in the mucosa of the small intestine are poorly understood.ObjectiveTo determine whether schlafen 3 (but not other schlafen proteins) act in vivo and whether its effects are limited to the small intestine. We have previously demonstrated in nonmalignant rat intestinal IEC-6 cells that schlafen 3 levels correlate with the expression of various differentiation markers in vitro in response to differentiation stimuli.DesignRandomized controlled experiment.SettingAnimal science laboratory.ParticipantsMale Sprague-Dawley rats 8 to 13 weeks old.Main outcomes and measuresMessenger RNA (mRNA) from jejunal and colonic mucosa was isolated, and transcript levels of schlafen proteins 1, 2, 3, 4, 5, 13, and 14; sucrase isomaltase (SI); dipeptidyl peptidase 4 (Dpp4); glucose transporter type 2 (Glut2); and villin were measured by quantitative reverse transcriptase-polymerase chain reaction. We tested parallel variations in protein levels by Western blotting and Dpp4 enzyme activity.ResultsThe transcript level of schlafen 3 (Slfn3) correlated with the levels of the differentiation markers SI, Dpp4, Glut2, and villin. However, the expression of schlafen proteins 1, 2, 4, 5, 13, and 14 did not correlate with the expression of the differentiation markers. The mucosal mRNA levels of Slfn3, SI, Glut2, and Dpp4 were all substantially higher in the rat jejunum than in colonic mucosa by a mean (SE) factor of 51.0 (13.2) for 6 rats (P < .05), 599 (99) for 8 rats (P < .01), 12.5 (5.5) for 8 rats (P < .01), and 14.0 (3.9) for 8 rats (P < .01), respectively. In IEC-6 cells, infection with adenovirus-expressing GFP-tagged Slfn3 significantly increased Slfn3 expression and Dpp4-specific activity compared with GFP-expressing virus (in 6 rats; P < .05).Conclusions and relevanceTaken together with our previous in vitro observations, the results suggest that small intestinal enterocytic epithelial differentiation in rats may be regulated by Slfn3 in vivo, as in vitro, and that these effects may be specific to the small intestinal enterocytic phenotype as opposed to that of the mature colonocyte. Slfn3 human orthologs may be targeted to stimulate intestinal differentiation in patients with short bowel syndrome.

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Studies on the phospholipases of rat intestinal mucosa.

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