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Studies on the role of cAMP and its activation of cAMP-dependent protein kinase in the mediation of vascular smooth muscle relaxation Zammit, Danielle Christine
Abstract
The adenosine 3',5'-cyclic monophosphate (cAMP) activation of cAMP-dependent protein kinase (PKA), and its resultant effect on vascular smooth muscle tone was investigated. Isoproterenol (ISO) and prostaglandin E₁ ( PGE₁) have both been shown to elevate cAMP in vascular smooth muscle, the increase being accompanied by relaxation with ISO and contraction with P G E T . The activation of different pools of PKA by these drugs has been suggested to explain a similar observation in cardiomyocytes, where both ISO and PGE₁ elevated cAMP, yet only ISO increased contractility. To determine whether the circumstances in vascular smooth muscle were analogous to those in cardiac tissue, the study investigated the elevation of cAMP and the activation of PKA in subcellular fractions of vascular preparations treated with 1μM ISO and 10μM PGE₁. A 1μM forskolin (FSK)/ 10μM PGE₁ combination was used as a positive control for cAMP measurement. An integral component was the use of the rabbit aorta medial strip, consisting of only smooth muscle cells. It was not possible to observe PKA activation in any of these experiments. Studies in aortic strips denuded of the endothelium demonstrated a large increase in cAMP levels in response to the FSK/PGE₁ combination. ISO had no effect on cAMP levels in helical strips, although it relaxed phenylephrine-induced contractions. Contrary to observations in helical strips, no difference in cAMP levels was recorded in any cell fraction from the medial strips, with any of the drugs used. ISO relaxed medial strips, but cAMP assays present no evidence of an increase in cAMP being related to the relaxation of vascular smooth muscle. The results obtained are not sufficient to either support, or negate, the hypothesis that cAMP elevation and the subsequent activation of PKA plays an important role in vascular smooth muscle relaxation. The data suggest that a) it is possible to measure cAMP levels in different subcellular fractions of vascular smooth muscle and b) differences exist between the tunica media and the adventitia with respect to their functional and cAMP responses to these drugs. Further investigation of the functional compartmentation of cAMP and PKA in the cell, and the signalling systems in the different layers of the blood vessel wall may elucidate the role of the cAMP/PKA system in the control of vascular tone.
Item Metadata
Title |
Studies on the role of cAMP and its activation of cAMP-dependent protein kinase in the mediation of vascular smooth muscle relaxation
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1997
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Description |
The adenosine 3',5'-cyclic monophosphate (cAMP) activation of cAMP-dependent
protein kinase (PKA), and its resultant effect on vascular smooth
muscle tone was investigated. Isoproterenol (ISO) and prostaglandin E₁ ( PGE₁)
have both been shown to elevate cAMP in vascular smooth muscle, the increase
being accompanied by relaxation with ISO and contraction with P G E T . The
activation of different pools of PKA by these drugs has been suggested to
explain a similar observation in cardiomyocytes, where both ISO and PGE₁
elevated cAMP, yet only ISO increased contractility.
To determine whether the circumstances in vascular smooth muscle were
analogous to those in cardiac tissue, the study investigated the elevation of
cAMP and the activation of PKA in subcellular fractions of vascular preparations
treated with 1μM ISO and 10μM PGE₁. A 1μM forskolin (FSK)/ 10μM PGE₁
combination was used as a positive control for cAMP measurement. An integral
component was the use of the rabbit aorta medial strip, consisting of only
smooth muscle cells.
It was not possible to observe PKA activation in any of these experiments.
Studies in aortic strips denuded of the endothelium demonstrated a large
increase in cAMP levels in response to the FSK/PGE₁ combination. ISO had no
effect on cAMP levels in helical strips, although it relaxed phenylephrine-induced
contractions. Contrary to observations in helical strips, no difference in cAMP
levels was recorded in any cell fraction from the medial strips, with any of the drugs used. ISO relaxed medial strips, but cAMP assays present no evidence of
an increase in cAMP being related to the relaxation of vascular smooth muscle.
The results obtained are not sufficient to either support, or negate, the
hypothesis that cAMP elevation and the subsequent activation of PKA plays an
important role in vascular smooth muscle relaxation. The data suggest that a) it
is possible to measure cAMP levels in different subcellular fractions of vascular
smooth muscle and b) differences exist between the tunica media and the
adventitia with respect to their functional and cAMP responses to these drugs.
Further investigation of the functional compartmentation of cAMP and PKA in the
cell, and the signalling systems in the different layers of the blood vessel wall
may elucidate the role of the cAMP/PKA system in the control of vascular tone.
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Extent |
3699811 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-03-19
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Provider |
Vancouver : University of British Columbia Library
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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.
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DOI |
10.14288/1.0087915
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1997-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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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.