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Functionally induced changes in water transport in the proximal tubule segment of rat kidneys.

Faarup P, Holstein-Rathlou NH, Nørgaard T, Harrison AP, Bastholm L, Thatt L, Johansen FF, Hegedüs V - Int J Nephrol Renovasc Dis (2011)

Bottom Line: However, in the second segment, a special cellular phenomenon was constantly present, comprising a significant intercellular space that was easily identified using a light microscope.In the third segment, in which the presence of basolateral interdigitations is minimal, the small lateral space, which was found to be present in cryopreparations between neighboring cells from the normal kidney, was found to be enlarged by heavy salt loading of short duration.It is concluded that these cryotechniques demonstrate quantitative structural variations between superficial and deep nephrons, as well as the presence of extracellular areas between the cells of the second and the third segment, representing a structural background for the essential transport of water from the proximal tubules to the peritubular capillaries.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Sciences, Panum Institute University of Copenhagen.

ABSTRACT
To eliminate freezing artifacts in the proximal tubule cells, two cryotechniques were applied to normal rat kidneys, ie, freeze substitution and special freeze drying. In addition, salt depletion and salt loading were applied to groups of rats to evaluate whether the segmental structure of the proximal tubule could be altered. In the superficial part of the renal cortex of normal kidneys, the typical first segment structure in the proximal tubule was generally present in the early postglomerular fraction of the tubule. However, in the second segment, a special cellular phenomenon was constantly present, comprising a significant intercellular space that was easily identified using a light microscope. In the third segment, in which the presence of basolateral interdigitations is minimal, the small lateral space, which was found to be present in cryopreparations between neighboring cells from the normal kidney, was found to be enlarged by heavy salt loading of short duration. It is concluded that these cryotechniques demonstrate quantitative structural variations between superficial and deep nephrons, as well as the presence of extracellular areas between the cells of the second and the third segment, representing a structural background for the essential transport of water from the proximal tubules to the peritubular capillaries.

No MeSH data available.


The percentage segmental distribution of the total loops from the proximal convoluted tubule of the renal cortex of freeze-substituted kidneys.Notes: 2A) In the superficially located nephrons of normal kidneys (Group 1A) the S2-like cells in the loops were significantly more frequent than the S1-, and S1-2 like cells, which were found to be equally frequent. Slight salt depletion or salt loading did not change these values significantly (Group 2A and B). However, after a heavy salt loading of short duration (Group 2C) the frequency of S2-like cells was elevated from about 40 % to more than 80 %. In accordance, the number of S1- and S1-2 like cells were reduced to around 10 % of the total. Moreover, even 4 weeks later in the Control (Groups 2F) values were found to return to those seen in normal kidneys (see “normal” - Group 1A). 2B) In juxtamedullary located nephrons in freeze-substituted kidneys the normal kidneys (Group A) revealed a number of S1-like cells that were slightly lower than those in the superficial nephrons (Graph 2A), otherwise, the distribution was rather similar. No significant changes were found with moderate salt depletion or salt loading (Groups 2A and B). However, a heavy salt loading of short duration (Group 2C) induced the number of S2-like cells to become clearly elevated in percentage terms. S1-like and S1-2 like cells were concomitantly reduced in proportion. Notably though these structural changes did not normalize, even in the Controls up to 4 weeks later (Group 2F).
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f12-ijnrd-4-073: The percentage segmental distribution of the total loops from the proximal convoluted tubule of the renal cortex of freeze-substituted kidneys.Notes: 2A) In the superficially located nephrons of normal kidneys (Group 1A) the S2-like cells in the loops were significantly more frequent than the S1-, and S1-2 like cells, which were found to be equally frequent. Slight salt depletion or salt loading did not change these values significantly (Group 2A and B). However, after a heavy salt loading of short duration (Group 2C) the frequency of S2-like cells was elevated from about 40 % to more than 80 %. In accordance, the number of S1- and S1-2 like cells were reduced to around 10 % of the total. Moreover, even 4 weeks later in the Control (Groups 2F) values were found to return to those seen in normal kidneys (see “normal” - Group 1A). 2B) In juxtamedullary located nephrons in freeze-substituted kidneys the normal kidneys (Group A) revealed a number of S1-like cells that were slightly lower than those in the superficial nephrons (Graph 2A), otherwise, the distribution was rather similar. No significant changes were found with moderate salt depletion or salt loading (Groups 2A and B). However, a heavy salt loading of short duration (Group 2C) induced the number of S2-like cells to become clearly elevated in percentage terms. S1-like and S1-2 like cells were concomitantly reduced in proportion. Notably though these structural changes did not normalize, even in the Controls up to 4 weeks later (Group 2F).

Mentions: In terms of a quantitative analysis of the cells in the juxtamedullary region, ie, in the immediate postglomerular neck region of the normal kidney, the S1 segments were found to be significantly fewer in number than those measured superficially (see Graph 1A compared with Graph 1B, Group 1A). However, a total count of the convoluted proximal tubule showed a difference between superficial and juxtamedullary nephrons (significantly lower numbers of S1 segment loops) for the juxtamedullary nephrons alone (see Graph 2A compared with Graph 2B, Group 1A). In the vitally stained, freeze-dried specimens (free of fixation, water contamination, and embedding media artifact), a similar structure was observed to that of the freeze-substituted specimens with regard to the S1 and S2 loops (Figure 3).


Functionally induced changes in water transport in the proximal tubule segment of rat kidneys.

Faarup P, Holstein-Rathlou NH, Nørgaard T, Harrison AP, Bastholm L, Thatt L, Johansen FF, Hegedüs V - Int J Nephrol Renovasc Dis (2011)

The percentage segmental distribution of the total loops from the proximal convoluted tubule of the renal cortex of freeze-substituted kidneys.Notes: 2A) In the superficially located nephrons of normal kidneys (Group 1A) the S2-like cells in the loops were significantly more frequent than the S1-, and S1-2 like cells, which were found to be equally frequent. Slight salt depletion or salt loading did not change these values significantly (Group 2A and B). However, after a heavy salt loading of short duration (Group 2C) the frequency of S2-like cells was elevated from about 40 % to more than 80 %. In accordance, the number of S1- and S1-2 like cells were reduced to around 10 % of the total. Moreover, even 4 weeks later in the Control (Groups 2F) values were found to return to those seen in normal kidneys (see “normal” - Group 1A). 2B) In juxtamedullary located nephrons in freeze-substituted kidneys the normal kidneys (Group A) revealed a number of S1-like cells that were slightly lower than those in the superficial nephrons (Graph 2A), otherwise, the distribution was rather similar. No significant changes were found with moderate salt depletion or salt loading (Groups 2A and B). However, a heavy salt loading of short duration (Group 2C) induced the number of S2-like cells to become clearly elevated in percentage terms. S1-like and S1-2 like cells were concomitantly reduced in proportion. Notably though these structural changes did not normalize, even in the Controls up to 4 weeks later (Group 2F).
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Related In: Results  -  Collection

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f12-ijnrd-4-073: The percentage segmental distribution of the total loops from the proximal convoluted tubule of the renal cortex of freeze-substituted kidneys.Notes: 2A) In the superficially located nephrons of normal kidneys (Group 1A) the S2-like cells in the loops were significantly more frequent than the S1-, and S1-2 like cells, which were found to be equally frequent. Slight salt depletion or salt loading did not change these values significantly (Group 2A and B). However, after a heavy salt loading of short duration (Group 2C) the frequency of S2-like cells was elevated from about 40 % to more than 80 %. In accordance, the number of S1- and S1-2 like cells were reduced to around 10 % of the total. Moreover, even 4 weeks later in the Control (Groups 2F) values were found to return to those seen in normal kidneys (see “normal” - Group 1A). 2B) In juxtamedullary located nephrons in freeze-substituted kidneys the normal kidneys (Group A) revealed a number of S1-like cells that were slightly lower than those in the superficial nephrons (Graph 2A), otherwise, the distribution was rather similar. No significant changes were found with moderate salt depletion or salt loading (Groups 2A and B). However, a heavy salt loading of short duration (Group 2C) induced the number of S2-like cells to become clearly elevated in percentage terms. S1-like and S1-2 like cells were concomitantly reduced in proportion. Notably though these structural changes did not normalize, even in the Controls up to 4 weeks later (Group 2F).
Mentions: In terms of a quantitative analysis of the cells in the juxtamedullary region, ie, in the immediate postglomerular neck region of the normal kidney, the S1 segments were found to be significantly fewer in number than those measured superficially (see Graph 1A compared with Graph 1B, Group 1A). However, a total count of the convoluted proximal tubule showed a difference between superficial and juxtamedullary nephrons (significantly lower numbers of S1 segment loops) for the juxtamedullary nephrons alone (see Graph 2A compared with Graph 2B, Group 1A). In the vitally stained, freeze-dried specimens (free of fixation, water contamination, and embedding media artifact), a similar structure was observed to that of the freeze-substituted specimens with regard to the S1 and S2 loops (Figure 3).

Bottom Line: However, in the second segment, a special cellular phenomenon was constantly present, comprising a significant intercellular space that was easily identified using a light microscope.In the third segment, in which the presence of basolateral interdigitations is minimal, the small lateral space, which was found to be present in cryopreparations between neighboring cells from the normal kidney, was found to be enlarged by heavy salt loading of short duration.It is concluded that these cryotechniques demonstrate quantitative structural variations between superficial and deep nephrons, as well as the presence of extracellular areas between the cells of the second and the third segment, representing a structural background for the essential transport of water from the proximal tubules to the peritubular capillaries.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Sciences, Panum Institute University of Copenhagen.

ABSTRACT
To eliminate freezing artifacts in the proximal tubule cells, two cryotechniques were applied to normal rat kidneys, ie, freeze substitution and special freeze drying. In addition, salt depletion and salt loading were applied to groups of rats to evaluate whether the segmental structure of the proximal tubule could be altered. In the superficial part of the renal cortex of normal kidneys, the typical first segment structure in the proximal tubule was generally present in the early postglomerular fraction of the tubule. However, in the second segment, a special cellular phenomenon was constantly present, comprising a significant intercellular space that was easily identified using a light microscope. In the third segment, in which the presence of basolateral interdigitations is minimal, the small lateral space, which was found to be present in cryopreparations between neighboring cells from the normal kidney, was found to be enlarged by heavy salt loading of short duration. It is concluded that these cryotechniques demonstrate quantitative structural variations between superficial and deep nephrons, as well as the presence of extracellular areas between the cells of the second and the third segment, representing a structural background for the essential transport of water from the proximal tubules to the peritubular capillaries.

No MeSH data available.