Biologia, Bratislava 54/Suppl. 6: 177-181, 1999.
ISSN 0006-3088 (Biologia). ISSN 1335-6399 (Biologia. Section Cellular and Molecular Biology).
Local anesthetic heptacaine inhibited potassium channel from tracheal microsomes.
Tatjana Cemanova1, Marta Gaburjakova2, Jens Schlossmann3, Elena Ondriasova1& Karol Ondrias2*
1 Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University, Odbojarov 10, SK-83232 Bratislava, Slovakia
2 Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Vlarska 5, SK-83334 Bratislava, Slovakia; tel.: ++421 7 5477 4102, fax: ++421 7 5477 3666, e-mail: email@example.com
3 Technische Universitat, Institut fur Pharmakologie und Toxikologie, Biedersteiner Strasse 29, D-80802 Munchen, Germany
* corresponding author
Received: December 15, 1998 / Accepted: October 5, 1999
Single channel properties of potassium channels from microsomal membranes isolated from bovine trachea were studied in bilayer lipid membrane (BLM). After incorporation of tracheal microsomal membranes into BLM, single channels permeable for potassium were observed. Conductance of the channel, at 800 mmol/L KCl (or 1.2 mol/L KCl) and 200 nmol/L Ca2+ in the cis side versus 50 mmol/L KCl and 53 mmol/L Ca(OH)2 in the trans side, was 187 pS (or 234 pS). Its open probability (P-open) varied and was in the range of 0.55-0.87. Heptacaine (100 mmol/L) decreased the open probability of the potassium channel from 0.59 to 0.20. Further increase in heptacaine concentrations to 300 mmol/L decreased P-open to 0.17. At 800 mmol/L heptacaine concentration the channel was blocked and a noisy, nonregular current through BLM was induced. We suppose that the inhibitory effect of heptacaine is a result of direct drug-channel interaction and that its induction of non-regular current is a result of drug nonspecific membrane perturbation.
Key words: heptacaine, single channel, potassium channel, trachea, bilayer lipid membrane.