Section 7
Chapter 6,490

Structural and functional organization of the brush border membrane in the rainbow trout salmo gairdneri intestine

D.C.stanzo G.; Florentz, A.; Leray, C.; Nonnotte, L.

Molecular Physiology 4(3-4): 111-124


Accession: 006489571

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The disbribution pattern of some enzyme activities was determined in the 2 main parts of the trout intestine. Maltase and glutamyl transpeptidase were more active in the anterior part. The same pattern was observed for alkaline phosphatase, cytochrome oxidase, various ATPases and 5'-nucleotidase. The bursh border membranes, isolated by a method based on hypotonic lysis and Mg2+-aggregation of contaminants, were in an acceptable state of purity only when the mucosa was collected from the anterior intestine. Only that region gave, at the ultrastructural level, homogeneous preparations of brush border membrane vesicles without other identified organelles. This observation was compared with the morphology of the apical part of enterocytes. The co-purification of some (Na+K+)-ATPase together with 5'-nucleotidase activities may reflect their presence at the luminal border of enterocytes. The lipid composition was established: phospholipids, total cholesterol and proteins were in the weight ratio of 28:15:57. The amount of individual phospholipids was quantitated. A phosphatidylinositol [PI] content (20% of all phospholipids) twice as high as that determined in mammals was found. Individual phospholipids had a distinct fatty acid composition and amoung the 3 main fractions (PC [phosphatidylcholine] PE [phosphatidylethanolamine] and PI) quantitative differences were seen both in saturated and unsaturated fatty acid composition. A high percentage (23-34%) of essential polyunsaturated fatty acids (n-3 family) was found.

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