Effect of agmatine on intracellular free calcium concentration in isolated rat ventricular myocytes

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Journal Title:
ACTA PHYSIOLOGICA SINICA
Issue:
Volume 54, Issue 06, 2002
DOI:
Key Word:
agmatine;fluorescence intensity;myocytes;intracellular calcium;Ca2+ channel;intracellular Ca2+ release;confocal microscopy

Abstract: The present study was to investigate the effects of agmatine (Agm) on free intracellular calcium concentration ([Ca2+]i) of isolated rat ventricular myocytes. [Ca2+]i was measured by confocal microscopy in single rat ventricular myocytes which were dissociated by enzymatic dissociation method and loaded with Fluo 3-AM. The changes in [Ca2+]i were represented by fluorescence intensity (FI) or relative fluorescence intensity (F/F0%). The results showed that the control level of FI value of single rat ventricular myocytes was 128.8±13.8 and 119.6±13.6 in the presence of normal Tyrode′s solution containing Ca2+ 1.0 mmol/L and Ca2+-free Tyrode′s solution, respectively. There was no difference between these two groups (P>0.05). Agm 0.1, 1, and 10 mmol/L significantly reduced the [Ca2+]i in both extracellular solutions in a concentration-dependent manner. The similar effect of Agm on [Ca2+]i was also observed in the presence of EGTA 3 mmol/L. KCl 60 mmol/L, PE 30 μmol/L, and Bay-K-8644 10 μmol/L, all these substances induced [Ca2+]i elevations in ventricular myocytes. Agm (0.1, 1, and 10 mmol/L) markedly inhibited the increase in [Ca2+]i induced by KCl, phenylephrine (PE), and Bay-K-8644. When Ca2+ waves were produced by increasing extracellular Ca2+ concentration from 1 to 10 mmol/L, 1 mmol/L Agm could block the propagating waves of elevated [Ca2+]i, and reduce the velocity and duration of propagating waves. These results suggest that Agm possesses an inhibitory effects on [Ca2+]i via blocking voltage-dependent Ca2+ channel, and possibly by alleviating calcium release from SR in single isolated rat ventricular myocytes.

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