Abstract
In electrically stimulated myocytes loaded with the fluorescent Ca2+ indicator indo 1-acetoxymethyl ester, spermine induced a dose-dependent (100- 500 μM) negative inotropic effect, which was associated with a decrease in the magnitude of the cytosolic Ca2+ concentration ([Ca2+](i)) transient but not with changes in myofilament responsiveness to Ca2+. Spermidine induced a less pronounced negative inotropic effect, whereas putrescine did not modify myocyte contraction. In the unstimulated state, spermine did not alter resting [Ca2+](i). Superfusion of the cardiac myocytes with 10 mM α- difluoromethylornithine, an inhibitor of polyamine synthesis, did not modify cellular responses to isoproterenol (10-9-10-7 M). β-Adrenergic stimulation did not affect either ornithine decarboxylase activity or intracellular polyamine levels within a 10-s to 15-min period of treatment. In summary, only exogenously administered polyamines were able to influence myocyte contractility. Their negative inotropic effect resulted from changes in [Ca2+](i) homeostasis and required cellular depolarization.
Original language | English |
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Journal | American Journal of Physiology - Heart and Circulatory Physiology |
Volume | 267 |
Issue number | 2 36-2 |
Publication status | Published - 1994 |
Keywords
- α-difluoromethylornithine
- β-adrenergic stimulation
- cytosolic calcium
- indo 1
- ornithine decarboxylase
ASJC Scopus subject areas
- Physiology
- Agricultural and Biological Sciences(all)
- Medicine(all)