An investigation has been carried out into the effects of extracellular calcium on cyclic nucleotide levels in rat ventricle. Increasing extracellular calcium, over the range which directly affected contractility, produced a concentration related increase in the level of cyclic AMP. Positive correlations were found between extracellular calcium and cyclic AMP; and between cyclic AMP and isometrically developed tension. No reciprocal relationships were found for cyclic GMP over the same calcium concentration range. Increasing extracellular calcium above the maximal inotropic concentration did not produce a further increase in cyclic AMP, although increases in cyclic GMP were noted. Calcium slow channel antagonists, nifedipine and manganese both depressed developed tension at the concentrations used, but this effect was not associated with any significant change in cyclic nucleotide levels. Verapamil depressed developed tension and cyclic AMP levels but the effect on cyclic AMP was not concentration related. No calcium slow channel antagonist significantly affected cyclic GMP levels. In electrically paced hearts, increasing rate of stimulation depressed developed tension but had no significant effect on cyclic AMP.
|Number of pages||12|
|Journal||Journal of Molecular and Cellular Cardiology|
|State||Published - Sep 1981|
Bibliographical noteFunding Information:
We thank Abbott Laboratories Ltd, for verapamil, Bayer Pharmaceuticals for nifedipine, and Dr D. M. Yellon (Myocardial Metabolism Laboratory, St Thomas’ Hospital) for cyclic AMP binding protein. This work is supported by the British Heart Foundation and the University of Bath Research Fund.
- Ca slow channel antagonists
- Cyclic AMP
- Cyclic GMP
- Developed tension
- Heart rate
- Rat ventricle
ASJC Scopus subject areas
- Molecular Biology
- Cardiology and Cardiovascular Medicine