Properties of a new calcium-permeable single channel from tracheal microsomes

• Published in: Biochimica et biophysica acta 1999-02, Vol.1417 (1), p.25-31
• Main Authors: Gaburjáková, Marta, Schlossmann, Jens, Ondriaš, Karol
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - pharmacology; Animals; Calcium - metabolism; Calcium channel; Calcium Channels - chemistry; Calcium Channels - drug effects; Calcium Channels - isolation & purification; Cattle; Heparin - pharmacology; Intracellular Membranes - chemistry; Intracellular Membranes - metabolism; Lipid bilayer; Lipid Bilayers - chemistry; Microsome; Microsomes - metabolism; Ruthenium Red - pharmacology; Single channel; Trachea; Trachea - metabolism
• ISSN: 0005-2736; 0006-3002; 1879-2642
• DOI: 10.1016/S0005-2736(98)00246-6

After the incorporation of the tracheal microsomal membrane into bilayer lipid membrane (BLM), a new single channel permeable for calcium was observed. Using the BLM conditions, 53 mM Ca 2+ in trans solution versus 200 nM Ca 2+ in cis solution, the single calcium channel current at 0 mV was 1.4–2.1 pA and conductance was 62–75 pS. The channel Ca 2+/K + permeability ratio was 4.8. The open probability ( P-open) was in the range of 0.7–0.97. The P-open, measured at −10 mV to +30 mV ( trans- cis), was not voltage dependent. The channel was neither inhibited by 10–20 μM ruthenium red, a specific blocker of ryanodine calcium release channel, nor by 10–50 μM heparin, a specific blocker of IP 3 receptor calcium release channel, and its activity was not influenced by addition of 0.1 mM MgATP. We suggest that the observed new channel is permeable for calcium, and it is neither identical with the known type 1 or 2 ryanodine calcium release channel, nor type 1 or 2 IP 3 receptor calcium release channel.