Properties of a Mg2+-dependent, and Ca2+-inhibited ATPase localized in the brush border of the surface epithelial syncytium of a parasitic flatworm

1981 ◽  
Vol 59 (6) ◽  
pp. 918-923 ◽  
Author(s):  
M. Saidur Rahman ◽  
D. F. Mettrick ◽  
R. B. Podesta
Keyword(s):  
Atpase Activity ◽  
Osmotic Pressure ◽  
Brush Border ◽  
Volume Regulation ◽  
Brush Border Membrane ◽  
Ethacrynic Acid ◽  
Surface Membrane ◽  
Hymenolepis Diminuta ◽  
Parasitic Flatworm ◽  
Acid Reaction

The brush border membrane of the surface epithelial syncytium of the parasitic flatworm, Hymenolepis diminuta, was isolated by saponin treatment, and the ATPase activity was determined. The ATPase activity was insensitive to ouabain, SCN−, HCO3−, ethanol, and, although slightly inhibited by high oligomycin concentrations, was inhibited by ethacrynic acid. Reaction mixtures made increasingly hypertonic with mannitol resulted in vesicular changes in the microvilli and decreased ATPase activity. Although treatment of the brush border fraction with deoxycholate increased ATPase activity, the dependence of activity on the osmotic pressure of the reaction mixture persisted in the solubilized membrane preparations. ATPase activity was dependent upon Mg2+ and Na+ + K+ concentration. It is suggested that the ATPase in the flatworm surface membrane is involved in volume regulation in hypotonic media.

Use of saponin in the preparation of brush border from a parasitic flatworm

1981 ◽  
Vol 59 (6) ◽  
pp. 911-917 ◽  
Author(s):  
M. S. Rahman ◽  
D. F. Mettrick ◽  
R. B. Podesta
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Hymenolepis Diminuta ◽  
Parasitic Flatworm ◽  
Basal Plasma Membrane ◽  
Basal Plasma

Saponin treatment in hypotonic or hypertonic fluids, followed by vibration, was used to isolate the brush border membrane from the surface epithelial syncytium of Hymenolepis diminuta. Electron microscopy of the membrane pellets and the parasites indicated that the area of the syncytium sheered by vibration of the parasites was correlated with the areas of the syncytium in which there occurred the greatest amount of osmotically induced swelling: below and adjacent to the brush border in hypotonic incubation, and the infoldings of the basal plasma membrane of the syncytium in hypertonic incubations. Vesiculation of the microvilli occurred in incubations made hypertonic with mannitol.

Immunolocalization of NHE8 in rat kidney

2005 ◽  
Vol 288 (3) ◽  
pp. F530-F538 ◽  
Author(s):  
Sunita Goyal ◽  
SueAnn Mentone ◽  
Peter S. Aronson
Keyword(s):  
Proximal Tubule ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Rat Kidney ◽  
Surface Membrane ◽  
Proximal Tubules ◽  
Intense Staining ◽  
Proximal Tubule Cells ◽  
Nephron Segment ◽  
Tubule Cells

In situ hybridization studies demonstrated that Na+/H+ exchanger NHE8 is expressed in kidney proximal tubules. Although membrane fractionation studies suggested apical brush-border localization, precise membrane localization could not be definitively established. The goal of the present study was to develop isoform-specific NHE8 antibodies as a tool to directly establish the localization of NHE8 protein in the kidney by immunocytochemistry. Toward this goal, two sets of antibodies that label different NHE8 epitopes were developed. Monoclonal antibody 7A11 and polyclonal antibody Rab65 both specifically labeled NHE8 by Western blotting as well as by immunofluorescence microscopy. The immunolocalization pattern in the kidney seen with both antibodies was the same, thereby validating NHE8 specificity. In particular, NHE8 expression was observed on the apical brush-border membrane of all proximal tubules from S1 to S3. The most intense staining was evident in proximal tubules in the deeper cortex and medulla with a significant but somewhat weaker staining in superficial proximal tubules. Colocalization studies with γ-glutamyltranspeptidase and megalin indicated expression of NHE8 on both the microvillar surface membrane and the coated-pit region of proximal tubule cells, suggesting that NHE8 may be subject to endocytic retrieval and recycling. Although colocalizing in the proximal tubule with NHE3, no significant alteration in NHE8 protein expression was evident in NHE3-null mice. We conclude that NHE8 is expressed on the apical brush-border membrane of proximal tubule cells, where it may play a role in mediating or regulating ion transport in this nephron segment.

scholarly journals Isolation of membrane-bound renal enzymes that metabolize kinins and angiotensins

1976 ◽  
Vol 157 (3) ◽  
pp. 643-650 ◽  
Author(s):  
P E Ward ◽  
E G Erdös ◽  
C D Gedney ◽  
R M Dowben ◽  
R C Reynolds
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Proximal Tubule ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Rat Kidney ◽  
Surface Membrane ◽  
Renal Kallikrein ◽  
Proximal Tubular ◽  
Kallikrein Activity

Cortex of rat kidney was homogenized and fractions enriched in plasma membrane, endoplasmic reticulum or brush border were prepared by several techniques of differential centrifugation. The identity and homogeneity of the membrane fragments were investigated by assaying marker enzymes and by transmission and scanning electron microscopy. Kallikrein was present in both plasma-membrane- and endoplasmic-reticulum-enriched fractions isolated by two fractionation procedures. Kallikrein was highly concentrated in a plasma-membrane fraction but was absent from the brush-border membrane of proximal tubular cells. Cells of transplanted renal tumours of the rat, originating from the proximal tubule, had no kallikrein activity. Kininase activity, angiotensin I-converting enzyme (kininase II) and angiotensinase were found in a plasma-membrane-enriched fraction and especially in the fraction containing isolated brush border. It is suggested that after renal kallikrein is synthesized on endoplasmic reticulum, it is subsequently reoriented to a surface membrane for activation and release. Renal kallikrein may enter the tubular filtrate distal to the proximal tubules. The brush-border membrane of proximal tubule is the major site of inactivation of kinins and angiotensin II..

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