Effect of hypermagnesemia on rat jejunal sodium and water transport

1976 ◽  
Vol 231 (6) ◽  
pp. 1771-1776 ◽  
Author(s):  
GF DiBona ◽  
LL Sawin
Keyword(s):  
Proximal Tubule ◽  
Water Transport ◽  
Renal Proximal Tubule ◽  
Epithelial Tissue ◽  
Rat Jejunum ◽  
Water Reabsorption ◽  
Sodium Influx ◽  
Sodium Efflux ◽  
Rat Renal Proximal Tubule

Hypermagnesemia decreases sodium and water reabsorption in the rat renal proximal tubule. To further understand this action, the effect of hypermagnesemia on sodium and water transport in the in vivo perfused rat jejunum was studied. The rat jejunum was chosen as another transporting epithelial tissue in the same species with unidirectional sodium flux characteristics similar to the rat renal proximal tubule, i.e., leaky as opposed to tight. Hypermagnesemia decreased net jejunal sodium and water reabsorption. This decrease was due to a reduction in unidirectional sodium efflux from lumen to blood and not to an increase in unidirectional sodium influx from blood to lumen. Hypermagnesemia did not change the jejunal permeability to inulin. The effect of hypermagnesemia on jejunal sodium and water transport is similar to that renal proximal tubule sodium and water transport. This similarity suggests that the mechanism of action of magnesium of these two transporting epithelial tissues is similar.

The Fine Structure of Rat Renal Microbodies and Cytoplasmic Bodies Following Perfusion Fixation

1973 ◽  
Vol 31 ◽  
pp. 620-621
Author(s):  
J. M. Barrett ◽  
P. M. Heidger
Keyword(s):  
Fine Structure ◽  
Proximal Tubule ◽  
Rat Kidney ◽  
Renal Proximal Tubule ◽  
Convincing Evidence ◽  
Cytoplasmic Bodies ◽  
Rat Renal Proximal Tubule ◽  
Renal Proximal Tubule Cells ◽  
Perfusion Fixation

Microbodies have received extensive morphological and cytochemical investigation since they were first described by Rhodin in 1954. To our knowledge, however, all investigations of microbodies and cytoplasmic bodies of rat renal proximal tubule cells have employed immersion fixation. Tisher, et al. have shown convincing evidence of fine structural alteration of microbodies in rhesus monkey kidney following immersion fixation; these alterations were not encountered when in vivo intravascular perfusion was employed. In view of these studies, and the fact that techniques for perfusion fixation have been established specifically for the rat kidney by Maunsbach, it seemed desirable to employ perfusion fixation to study the fine structure and distribution of microbodies and cytoplasmic bodies within the rat renal proximal tubule.

scholarly journals Dipeptidyl peptidase IV inhibition downregulates Na+-H+exchanger NHE3 in rat renal proximal tubule

2008 ◽  
Vol 294 (2) ◽  
pp. F414-F422 ◽  
Author(s):  
Adriana Castello Costa Girardi ◽  
Lívia Emy Fukuda ◽  
Luciana Venturini Rossoni ◽  
Gerhard Malnic ◽  
Nancy Amaral Rebouças
Keyword(s):  
Proximal Tubule ◽  
Brush Border ◽  
Membrane Vesicles ◽  
Dipeptidyl Peptidase ◽  
Renal Proximal Tubule ◽  
Dipeptidyl Peptidase Iv ◽  
Rat Renal Proximal Tubule ◽  
Sodium Hydrogen Exchanger ◽  
Male Wistar Rats

In the microvillar microdomain of the kidney brush border, sodium hydrogen exchanger type 3 (NHE3) exists in physical complexes with the serine protease dipeptidyl peptidase IV (DPPIV). The purpose of this study was to explore the functional relationship between NHE3 and DPPIV in the intact proximal tubule in vivo. To this end, male Wistar rats were treated with an injection of the reversible DPPIV inhibitor Lys [Z(NO2)]-pyrrolidide (I40; 60 mg·kg−1·day−1ip) for 7 days. Rats injected with equal amounts of the noninhibitory compound Lys[Z(NO2)]-OH served as controls. Na+-H+exchange activity in isolated microvillar membrane vesicles was 45 ± 5% decreased in rats treated with I40. Membrane fractionation studies using isopycnic centrifugation revealed that I40 provoked redistribution of NHE3 along with a small fraction of DPPIV from the apical enriched microvillar membranes to the intermicrovillar microdomain of the brush border. I40 significantly increased urine output (67 ± 9%; P < 0.01), fractional sodium excretion (63 ± 7%; P < 0.01), as well as lithium clearance (81 ± 9%; P < 0.01), an index of end-proximal tubule delivery. Although not significant, a tendency toward decreased blood pressure and plasma pH/HCO3−was noted in I40-treated rats. These findings indicate that inhibition of DPPIV catalytic activity is associated with inhibition of NHE3-mediated NaHCO3reabsorption in rat renal proximal tubule. Inhibition of apical Na+-H+exchange is due to reduced abundance of NHE3 protein in the microvillar microdomain of the kidney brush border. Moreover, this study demonstrates a physiologically significant interaction between NHE3 and DPPIV in the intact proximal tubule in vivo.

Axial heterogeneity in the rat proximal convoluted tubule. I. Bicarbonate, chloride, and water transport

1984 ◽  
Vol 247 (5) ◽  
pp. F816-F821 ◽  
Author(s):  
F. Y. Liu ◽  
M. G. Cogan
Keyword(s):  
Proximal Tubule ◽  
Water Transport ◽  
Wistar Rats ◽  
Proximal Convoluted Tubule ◽  
Free Flow ◽  
Concentration Profiles ◽  
Transport Capacity ◽  
Water Reabsorption ◽  
Substrate Concentrations

To measure simultaneously the concentration profiles of bicarbonate, chloride and inulin along the length of the superficial proximal convoluted tubule, free-flow micropuncture measurements were made sequentially from the end-proximal tubule to Bowman's space in 10 tubules of hydropenic Munich-Wistar rats. Bicarbonate and volume reabsorption were 354 +/- 21 pmol X mm-1 X min-1 and 5.9 +/- 0.4 nl X mm-1 X min-1 in the first millimeter and fell progressively in the remaining 3.8 mm of tubule, averaging 83 +/- 4 pmol X mm-1 X min-1 and 2.3 +/- 0.5 nl X mm-1 X min-1, respectively. The values in the initial millimeter represents a high transport capacity since they exceed rates that have been observed when comparable or even higher mean luminal substrate concentrations were presented to the late proximal tubule. In contrast, chloride reabsorption was only 206 +/- 55 peq X mm-1 X min-1 in the first millimeter compared with a mean of 306 +/- 22 peq X mm-1 X min-1 in the rest of the tubule. In conclusion, there is substantial axial transport heterogeneity, with bicarbonate and water reabsorption higher but chloride reabsorption lower in the early compared with the late superficial proximal convoluted tubule.

Hormonal regulation of rat renal proximal tubule brush-border membrane ionic permeability

1992 ◽  
Vol 263 (1) ◽  
pp. F144-F151 ◽  
Author(s):  
M. S. Lipkowitz ◽  
R. D. London ◽  
J. C. Beck ◽  
R. G. Abramson
Keyword(s):  
Parathyroid Hormone ◽  
Proximal Tubule ◽  
Brush Border ◽  
Renal Proximal Tubule ◽  
Ionic Permeability ◽  
Brush Border Membranes ◽  
Rat Renal Proximal Tubule ◽  
Selective Increase ◽  
Gi Proteins ◽  
Cl Permeability

The effects on ionic permeability of toxins and hormones that activate or deactivate the guanine nucleotide regulatory (G) proteins that govern adenylate cyclase activity were examined in rat renal proximal tubule cell brush-border membranes. These studies demonstrate that activation of stimulatory G (Gs) proteins by cholera toxin or parathyroid hormone and deactivation of inhibitory (G (Gi) proteins by pertussis toxin result in a selective increase in Cl- permeability relative to that of K+ as determined with the potential-sensitive fluorescent probe 3,3'-dipropylthiadicarbocyanine iodide [diS-C3-(5)]. In contrast, activation of Gi by angiotensin II significantly decreases relative Cl- permeability. The selective increase in relative Cl- permeability induced by parathyroid hormone results in an inside-negative potential in membrane vesicles exposed to an inward NaCl gradient that is of sufficient magnitude to stimulate electrogenic, Na(+)-dependent glucose transport. These data suggest that the relative ionic permeabilities of brush-border membranes are tonically regulated by the opposing effects of hormones that act via Gs or Gi proteins. Changes in membrane potential resulting from this regulation may play an important role in modifying transport in the proximal tubule.

Partial recovery of in vivo function by improved incubation conditions of isolated renal proximal tubule.

1997 ◽  
Vol 434 (4) ◽  
pp. 373-382 ◽  
Author(s):  
S. Müller-Berger ◽  
S. Coppola ◽  
I. Samaržija ◽  
G. Seki ◽  
E. Frömter
Keyword(s):  
Proximal Tubule ◽  
Renal Proximal Tubule ◽  
Partial Recovery
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