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Updated: Apr 15, 2026

Determination of the Relative Cell Surface and Total Expression of Recombinant Ion Channels Using Flow Cytometry
Published on: September 28, 2016
Nucleotides maintain the activity of Cav1.2 channels in guinea-pig ventricular myocytes
Shu-yuan Liu1, Jian-jun Xu2, Etsuko Minobe2
1Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China; Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan.
Abstract:
The activity of Cav1.2 Ca(2+) channels is maintained in the presence of calmodulin and ATP, even in cell-free patches, and thus a channel ATP-binding site has been suggested. In this study, we examined whether other nucleotides, such as GTP, UTP, CTP, ADP and AMP, could be substituted for ATP in guinea-pig ventricular myocytes. We found that all the nucleotides tested could re-prime the Ca(2+) channels in the presence of 1 μM calmodulin in the inside-out mode. The order of efficacy was ATP > GTP > UTP > ADP > CTP ≈ AMP. Thus, the presumed nucleotide-binding site in the channel seemed to favor a purine rather than pyrimidine base and a triphosphate rather than a di- or mono-phosphate group. Furthermore, a high concentration (10 mM) of GTP, UTP, CTP, ADP and AMP had inhibitory effects on the channel activity. These results provide information on the putative nucleotide-binding site(s) in Cav1.2 Ca(2+) channels.
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