Troponin I phosphorylation does not increase the rate of relaxation following laser flash photolysis of diazo-2 in guinea-pig skinned trabeculae |
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Authors: | Emma C Johns Sarah J Simnett I P Mulligan C C Ashley |
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Institution: | (1) University Laboratory of Physiology, Parks Road, Oxford, OX1 3PT, UK, GB;(2) Department of Cardiology, John Radcliffe Hospital, Oxford, OX3 9DU, UK, GB |
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Abstract: | In vivo, two effects of β-adrenergic stimulation in cardiac muscle are phosphorylation of troponin I and an increase in relaxation
rate. In vitro, cardiac TnI can be phosphorylated by protein kinase A (PKA). We have used the technique of laser flash photolysis
of the calcium chelator diazo-2 to investigate the effect of phosphorylation of TnI on the relaxation rate of skinned trabeculae
from the guinea-pig at 12°C. The fibres were phosphorylated by PKA, and double exponential curve fits of the average relaxation
transients showed no significant difference between the rate constants of the phosphorylated and control cases. We conclude
that TnI phosphorylation has no effect on the rate of relaxation in skinned trabeculae from the guinea-pig following diazo-2
photolysis.
Received: 30 October 1996 / Received after revision and accepted: 20 January 1997 |
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