- Library Home /
- Search Collections /
- Open Collections /
- Browse Collections /
- UBC Theses and Dissertations /
- Control of intracelluar Ca²⁺ in epithelial cells of...
Open Collections
UBC Theses and Dissertations
UBC Theses and Dissertations
Control of intracelluar Ca²⁺ in epithelial cells of the kidney thick ascending limb Dai, Long-jun
Abstract
The cortical thick ascending limb of Henle’s loop (cTAL) plays a fundamental role in salt reabsorption and concentration-dilution processes within the nephron. This study was performed to characterize the role of intracellular free Ca²⁺ ([Ca²⁺]i) in hormone-mediated signal transduction and to describe the function of Na⁺/Ca²⁺ exchange in control of [Ca²⁺]i in isolated cTAL cells from porcine kidney. Parathyroid hormone, arginine vasopressin, and atrial natriuretic peptide transiently increased [Ca²⁺]i, in a dose-dependent manner. The increment in [Ca²⁺]i induced by these hormones was by intracellular release and entry through plasma membrane Ca²⁺ channels. These hormone-induced Ca²⁺ transients were modulated by cAMP, cGMP, and PKC activation. In order for intracellular Ca²⁺ to play a role in signal transduction mechanisms it is necessary to have regulated processes which maintain [Ca²⁺]i at submicromolar levels. We evaluated the functional role of Na⁺/Ca²⁺ exchange in cTAL cells. cTAL cells treated with ouabain had basal [Ca²⁺]i 86±2 nM. Removal of external Na⁺ or voltage depolarization with KC1 resulted in rapid and reversible maximal elevation of [Ca²⁺]i 1023 ±72 nM (n=28), which was dependent on the presence of external Ca²⁺ and elevated [Na⁺]i. The activity of Na⁺/ Ca²⁺ exchange was modulated by protein phosphorylation as calmodulin inhibition decreased and phosphatase inhibition increased the apparent exchange activity. The presence of a Na⁺/ Ca²⁺ exchanger was confirmed with northern hybridization techniques. A gene transcript which encodes a portion of the intracellular ioop of the renal Na⁺/ Ca²⁺ exchanger was amplified from cortical tissue and cTAL cells by polymerase chain reaction (PCR) using primers flanking the alternative splicing site. Southern hybridization and DNA sequencing demonstrated the isoform contained exons B and D characteristic of one isoform (NACA3) of the renal Na⁺/ Ca²⁺ exchanger. The results provide both functional and molecular evidence for a N2aICa exchanger in cTAL cells of the porcine kidney. It is likely that Na⁺/ Ca²⁺ exchange plays an important role in [Ca²⁺]i control and thus hormonal regulation of electrolyte reabsorption within the cTAL cells.
Item Metadata
Title |
Control of intracelluar Ca²⁺ in epithelial cells of the kidney thick ascending limb
|
Creator | |
Publisher |
University of British Columbia
|
Date Issued |
1995
|
Description |
The cortical thick ascending limb of Henle’s loop (cTAL) plays a fundamental role in
salt reabsorption and concentration-dilution processes within the nephron. This study was
performed to characterize the role of intracellular free Ca²⁺ ([Ca²⁺]i) in hormone-mediated
signal transduction and to describe the function of Na⁺/Ca²⁺ exchange in control of [Ca²⁺]i
in isolated cTAL cells from porcine kidney. Parathyroid hormone, arginine vasopressin, and
atrial natriuretic peptide transiently increased [Ca²⁺]i, in a dose-dependent manner. The
increment in [Ca²⁺]i induced by these hormones was by intracellular release and entry
through plasma membrane Ca²⁺ channels. These hormone-induced Ca²⁺ transients were
modulated by cAMP, cGMP, and PKC activation. In order for intracellular Ca²⁺ to play
a role in signal transduction mechanisms it is necessary to have regulated processes which
maintain [Ca²⁺]i at submicromolar levels. We evaluated the functional role of Na⁺/Ca²⁺
exchange in cTAL cells. cTAL cells treated with ouabain had basal [Ca²⁺]i 86±2 nM.
Removal of external Na⁺ or voltage depolarization with KC1 resulted in rapid and
reversible maximal elevation of [Ca²⁺]i 1023 ±72 nM (n=28), which was dependent on the
presence of external Ca²⁺ and elevated [Na⁺]i. The activity of Na⁺/ Ca²⁺ exchange was
modulated by protein phosphorylation as calmodulin inhibition decreased and phosphatase
inhibition increased the apparent exchange activity. The presence of a Na⁺/ Ca²⁺ exchanger
was confirmed with northern hybridization techniques. A gene transcript which encodes
a portion of the intracellular ioop of the renal Na⁺/ Ca²⁺ exchanger was amplified from
cortical tissue and cTAL cells by polymerase chain reaction (PCR) using primers flanking
the alternative splicing site. Southern hybridization and DNA sequencing demonstrated
the isoform contained exons B and D characteristic of one isoform (NACA3) of the renal Na⁺/ Ca²⁺ exchanger. The results provide both functional and molecular evidence for a
N2aICa exchanger in cTAL cells of the porcine kidney. It is likely that Na⁺/ Ca²⁺
exchange plays an important role in [Ca²⁺]i control and thus hormonal regulation of
electrolyte reabsorption within the cTAL cells.
|
Extent |
2332465 bytes
|
Genre | |
Type | |
File Format |
application/pdf
|
Language |
eng
|
Date Available |
2009-04-16
|
Provider |
Vancouver : University of British Columbia Library
|
Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
|
DOI |
10.14288/1.0088109
|
URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
|
Graduation Date |
1995-11
|
Campus | |
Scholarly Level |
Graduate
|
Aggregated Source Repository |
DSpace
|
Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.