Authors: Pasi Tavi Matti Weckström Heikki Ruskoaho
Publish Date: 2000/08/15
Volume: 441, Issue: 1, Pages: 65-68
Abstract
The stretchinduced changes in contraction force cAMP and cGMP in isolated rat left atrium were studied Increasing the diastolic intraatrial pressure from 1 cmH2O to 8 cmH2O caused an immediate 500 ms increase in contraction force the magnitude of which was 224±029 n=6 times the force elicited by 1 cmH2O This was followed by a slower gradual increase of the force which was maximal 8 min after the stretch 433±031 n=6 These phenomena were not accompanied by changes in the cAMP n=24 or cGMP n=24 concentrations within the tissue at any duration of stretch tested 2 8 20 and 36 min n=6 at each time point Furthermore it was estimated that if the βadrenergic receptor agonist isoprenaline 100 nM was used to produce an increase of the contraction force of the same magnitude as that induced by stretch the cAMP concentration was greater 420±029 pmol/mg n=5 P0001 when compared to that produced after 20 min of stretch 269±012 pmol/mg n=6 Even without significantly changing the cGMP concentration isoprenaline significantly increased the cAMP/cGMP ratio 34±036 n=5 P001 compared to stretch 195±014 n=6 This result shows that in the rat atrium stretch does not regulate the production or breakdown of cyclic nucleotides cAMP or cGMP Thus it seems very unlikely that the effects of stretch on rat atrium function are caused by cAMP or cGMP
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