The link between myocardial contraction and relaxation: The effects of calcium antagonists

L. Vittone, H. E. Cingolani, R. A. Mattiazzi

Research output: Contribution to journalArticle

Abstract

In isolated rat hearts perfused at constant coronary flow and heart rate the amount of shortening in their major axis (L), the developed tension (T) and their time derivatives (Ĺ and Ṫ) were measured after different interventions. Relative changes of maximal velocities of contraction (+ Ĺ, + Ṫ) and relaxation (- Ĺ, - Ṫ) were assessed by the ratio between both velocities (+Ĺ/-Ĺ, + Ṫ/-Ṫ). After the interventions, cAMP intracellular levels and cAMP dependent protein kinase activity were measured. The negative inotropic effect of verapamil (10-7 m) and nifedipine (5×10-7 m) was accompanied by a relatively greater decrease in maximal velocity of relaxation. Consequently the ratio +Ĺ/-Ĺ increased. Verapamil increased + Ĺ/ - Ĺ from 1.27±0.07 to 1.57±0.08 (P2+ in the perfusate did not change the ratio +Ĺ/-Ĺ. A decrease in extracellular Ca2+, on the other hand, produced a greater decrease in -Ĺ than in +Ĺ, so that the ratio +Ĺ/-Ĺ increased from 1.27±0.05 to 1.49±0.10 (P2+ or isoproterenol can be used. However, for a given inotropic state, relaxation was faster when an increase in cAMP through the beta receptor stimulation was produced to overcome the negative inotropic state. The relatively greater effect of calcium antagonist compounds on relaxation can not be explained by a decrease in cAMP and its protein kinase activity. The mechanism might be related to a lower phospholamban phosphorylation through Ca2+-calmodulin activated protein kinase.

Original languageEnglish (US)
Pages (from-to)255-263
Number of pages9
JournalJournal of Molecular and Cellular Cardiology
Volume17
Issue number3
DOIs
StatePublished - 1985
Externally publishedYes

Fingerprint

Myocardial Contraction
Verapamil
Protein Kinases
Calcium Compounds
Calcium
Calmodulin
Cyclic AMP-Dependent Protein Kinases
Isoproterenol
Heart Rate
Phosphorylation
phospholamban
1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid dimethyl ester

Keywords

  • Ca-calmodulin activated protein kinase
  • Calcium antagonist compounds
  • cAMP dependent protein kinase
  • Inotropic state
  • Myocardial relaxation
  • Phospholamban phosphorylation

ASJC Scopus subject areas

  • Molecular Biology
  • Cardiology and Cardiovascular Medicine

Cite this

The link between myocardial contraction and relaxation : The effects of calcium antagonists. / Vittone, L.; Cingolani, H. E.; Mattiazzi, R. A.

In: Journal of Molecular and Cellular Cardiology, Vol. 17, No. 3, 1985, p. 255-263.

Research output: Contribution to journalArticle

Vittone, L. ; Cingolani, H. E. ; Mattiazzi, R. A. / The link between myocardial contraction and relaxation : The effects of calcium antagonists. In: Journal of Molecular and Cellular Cardiology. 1985 ; Vol. 17, No. 3. pp. 255-263.
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