Abstract
Smooth muscle was made permeable with α-toxin and β-escin. ATPase activity was measured using a phosphoenolpyruvate - pyruvate kinase regenerating system for ATP that was monitored by NADH fluorescence changes, and Ca2+ was measured using fura 2 fluorescence. α-Toxin-and β-escin-treated bundles of cells had a high ATPase activity, which was reduced 80% when exposed to 1% Triton X-100. This Triton-sensitive ATPase activity was increased by approximately 20% when GTP or GTPγS was added to the solutions and was of much greater magnitude than the Ca2+-activated ATPase associated with contraction. This high membrane ATPase activity will cause a gradient of ATP into and ADP out of the bundle of cells. Thus modulation of this ATPase by G-protein-receptor mechanisms could alter the force at a constant Ca2+ concentration by changing the ADP/ATP ratio within the cells. Measurements of the fura 2 fluorescence ratio (340/380) in α-toxin-treated bundles of cells following sudden changes in extracellular Ca2+ showed that the cells were not freely permeable to Ca EGTA. Similar experiments in β-escin-treated cells showed the cells to be much more permeable to Ca EGTA. These experiments indicate that great care must be taken in α-toxin- and β-escin-treated fibers to make sure that the intracellular ATP, ADP, and Ca2+ are held constant.
| Original language | English |
|---|---|
| Pages (from-to) | 1361-1367 |
| Number of pages | 7 |
| Journal | Canadian Journal of Physiology and Pharmacology |
| Volume | 72 |
| Issue number | 11 |
| State | Published - Dec 1 1994 |
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Keywords
- α-toxin
- β-escin
- ADP
- ATPase activity
- calcium ion activation
- force
- fura 2
- intracellular calcium
- skinned fibers
- smooth muscle
ASJC Scopus subject areas
- Physiology
- Pharmacology
Cite this
Relationship between ATPase activity, Ca2+, and force in α-toxin- and β-escin-treated smooth muscle. / Kerrick, W. Glenn; Hoar, P. E.
In: Canadian Journal of Physiology and Pharmacology, Vol. 72, No. 11, 01.12.1994, p. 1361-1367.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Relationship between ATPase activity, Ca2+, and force in α-toxin- and β-escin-treated smooth muscle
AU - Kerrick, W. Glenn
AU - Hoar, P. E.
PY - 1994/12/1
Y1 - 1994/12/1
N2 - Smooth muscle was made permeable with α-toxin and β-escin. ATPase activity was measured using a phosphoenolpyruvate - pyruvate kinase regenerating system for ATP that was monitored by NADH fluorescence changes, and Ca2+ was measured using fura 2 fluorescence. α-Toxin-and β-escin-treated bundles of cells had a high ATPase activity, which was reduced 80% when exposed to 1% Triton X-100. This Triton-sensitive ATPase activity was increased by approximately 20% when GTP or GTPγS was added to the solutions and was of much greater magnitude than the Ca2+-activated ATPase associated with contraction. This high membrane ATPase activity will cause a gradient of ATP into and ADP out of the bundle of cells. Thus modulation of this ATPase by G-protein-receptor mechanisms could alter the force at a constant Ca2+ concentration by changing the ADP/ATP ratio within the cells. Measurements of the fura 2 fluorescence ratio (340/380) in α-toxin-treated bundles of cells following sudden changes in extracellular Ca2+ showed that the cells were not freely permeable to Ca EGTA. Similar experiments in β-escin-treated cells showed the cells to be much more permeable to Ca EGTA. These experiments indicate that great care must be taken in α-toxin- and β-escin-treated fibers to make sure that the intracellular ATP, ADP, and Ca2+ are held constant.
AB - Smooth muscle was made permeable with α-toxin and β-escin. ATPase activity was measured using a phosphoenolpyruvate - pyruvate kinase regenerating system for ATP that was monitored by NADH fluorescence changes, and Ca2+ was measured using fura 2 fluorescence. α-Toxin-and β-escin-treated bundles of cells had a high ATPase activity, which was reduced 80% when exposed to 1% Triton X-100. This Triton-sensitive ATPase activity was increased by approximately 20% when GTP or GTPγS was added to the solutions and was of much greater magnitude than the Ca2+-activated ATPase associated with contraction. This high membrane ATPase activity will cause a gradient of ATP into and ADP out of the bundle of cells. Thus modulation of this ATPase by G-protein-receptor mechanisms could alter the force at a constant Ca2+ concentration by changing the ADP/ATP ratio within the cells. Measurements of the fura 2 fluorescence ratio (340/380) in α-toxin-treated bundles of cells following sudden changes in extracellular Ca2+ showed that the cells were not freely permeable to Ca EGTA. Similar experiments in β-escin-treated cells showed the cells to be much more permeable to Ca EGTA. These experiments indicate that great care must be taken in α-toxin- and β-escin-treated fibers to make sure that the intracellular ATP, ADP, and Ca2+ are held constant.
KW - α-toxin
KW - β-escin
KW - ADP
KW - ATPase activity
KW - calcium ion activation
KW - force
KW - fura 2
KW - intracellular calcium
KW - skinned fibers
KW - smooth muscle
UR - http://www.scopus.com/inward/record.url?scp=0028619934&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0028619934&partnerID=8YFLogxK
M3 - Article
C2 - 7767879
AN - SCOPUS:0028619934
VL - 72
SP - 1361
EP - 1367
JO - Canadian Journal of Physiology and Pharmacology
JF - Canadian Journal of Physiology and Pharmacology
SN - 0008-4212
IS - 11
ER -