Effect of agmatine on intracellular free calcium concentration in isolated rat ventricular myocytes.
The present study was to investigate the effects of agmatine (Agm) on free intracellular calcium concentration ([Ca(2+)]( i )) of isolated rat ventricular myocytes. [Ca(2+)]( 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 [Ca(2+)]( i ) were represented by fluorescence intensity (FI) or relative fluorescence intensity (F/F(0)%). 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 Ca(2+) 1.0 mmol/L and Ca(2+)-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 [Ca(2+)]( i ) in both extracellular solutions in a concentration-dependent manner. The similar effect of Agm on [Ca(2+)]( i ) was also observed in the presence of EGTA 3 mmol/L. KCl 60 mmol/L, PE 30 micromol/L, and Bay-K-8644 10 micromol/L, all these substances induced [Ca(2+)]( i ) elevations in ventricular myocytes. Agm (0.1, 1, and 10 mmol/L) markedly inhibited the increase in [Ca(2+)]( i ) induced by KCl, phenylephrine (PE), and Bay-K-8644. When Ca(2+) waves were produced by increasing extracellular Ca(2+) concentration from 1 to 10 mmol/L, 1 mmol/L Agm could block the propagating waves of elevated [Ca(2+)]( i ), and reduce the velocity and duration of propagating waves. These results suggest that Agm possesses an inhibitory effects on [Ca(2+)]( i ) via blocking voltage-dependent Ca(2+) channel, and possibly by alleviating calcium release from SR in single isolated rat ventricular myocytes.
Li
Qing
Q
Department of Physiology, Hebei Medical University, Shijiazhuang 050017.
Shang
Zhong-Lin
ZL
Yin
Jing-Xiang
JX
Wang
Yi-He
YH
He
Rui-Rong
RR
D000376:Agmatine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects; D002478:Cells, Cultured; D005260:Female; D006352:Heart Ventricles / Q000166:cytology; D008297:Male; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D015220:Calcium Channels; D000376:Agmatine; D002118:Calcium