K-Efflux in Koronararterien - Versuchsanordnung
Figure 1: Experimental assembly used for simulating ischaemia. Fig. redrawn from Gasser & Vaughan-Jones (1990). Schematic diagram of perfusion chamber. Ion-selective microelectrode (in our experiments e.g. Na+, pH, K+- selective microelectrode) pressed gently on the surface of a pig coronary artery strip and recording specific ion concentration changes during ischaemia. Preparation is laid across four supports (micropins, 100 µm in diameter) and pinned on one end and attached to a force transducer at the other. Also shown are two electrodes for field Stimulation. The diagram illustrates an episode of simulated ischaemia, with the preparation immersed almost completely in a stationary pool of paraffin oil (heavy stippling) while perfusion of warm (37 °C) Tyrode (light stippling) continues at the base of the chamber. Dashed lines represent ligated areas as described in the Methods.


Keywords: Arteria coronaria,  Arteria coronaria,  Efflux,  Efflux,  Graphische Darstellung,  ischaemia,  Ischämie,  Kalium,  microelectrode,  Mikroelektrode,  potassium

K-Efflux in Koronararterien - Mikroelektroden
Figure 2: Simplified diagram of different microelectrode tips during simulated ischaemia. Hatched area represents paraffin oil (P.o.), area underneath, marked with oval rings, represents myocardial or smooth muscle tissue (T). Between tissue and P.o. one can see the artificially created reduced extra-cellular space (ARECS). a. Electrode tip bevelled in a 45° angle not yielding ideal contact with the tissue surface, thus making contact with the paraffin oil. Under these conditions the hydrophobic carrier will instantly escape from the tip and the electrode does not give further readings. b. Elec-trode tip bevelled in a 45° angle pushed too deeply into the tissue causing cell damage. Cells will be either damaged or destroyed causing a constant leak of K+(K+ ions represented by stippling) into the ARECS which, in turn, leads to faulty measurements: instead of ischaemia-induced K+ efflux caused by changed K+ conductance of the membrane the electrode measures changes resulting from damaged cells (c.f. Fig. 3). c. Electrode tip bevelled in a 90° angle (flat tip) ideally positioned in the ARECS. Only under these circumstances correct measurements of transmembrane K+ efflux induced by ischaemia are possible (c.f. Fig. 3). d. Ideally bevelled surface microelectrode, impaled too deeply into the tissue. Stippling represents K+ ions leaking from damaged tissue - readings will be misleading. e. Too fine-tipped microelectrode, pushed too deeply into the tissue. Leaking K+ from the damaged tissue like in b and d, represented by stippling and small arrows.


Keywords: Arteria coronaria,  Arteria coronaria,  Efflux,  Efflux,  Graphische Darstellung,  ischaemia,  Ischämie,  Kalium,  microelectrode,  Mikroelektrode,  potassium

K-Efflux in Koronararterien
Figure 3: Guinea pig papillary muscle. Typical results when measuring K+ during an ischaemic episode. A. Experiment performed using an electrode bevelled with a 45° angle pushed too deeply into the preparation - penetrating approximately two or three layers of myocardial cells. Right handside panel: lack of effect of glibenclamide upon ischaemic K+ efflux in the same experiment, when microelectrode pushed too deeply into the tissue. B. Ideal experimental conditions: flat-tipped surface microelectrode gently touching the preparation like in Figure 2. Glibenclamide (100 microM) prevents early ischaemia-induced K+ efflux.


Keywords: Arteria coronaria,  Arteria coronaria,  Diagramm,  Efflux,  Efflux,  Glibenclamid,  glibenclamide,  ischaemia,  Ischämie,  Kalium,  potassium

K-Efflux in Koronararterien
Figure 4: Effect of glibenclamide during simulated ischaemia in an isolated pig coronary artery preparation. Glibenclamide (50 microM) reduces rate and extent of K+ efflux from the tissue. Left and right hand panel from the same preparation. Glibenclamide added 20 minutes before beginning of trace on the right hand side panel. Gap in trace represents 30 min


Keywords: Arteria coronaria,  Arteria coronaria,  Diagramm,  Efflux,  Efflux,  Glibenclamid,  glibenclamide,  ischaemia,  Ischämie,  Kalium,  potassium

K-Efflux in Koronararterien
Figure 5: Measurement of Na+ with Na+ selective microelectrode during simulated ischaemia in an isolated pig coronary artery strip. Na+s did not change throughout the ischaemic episode, indicating a steady state of transmembrane Na+-movement during early simulated ischaemia in this preparation. In the presence of glibenclamide (50 microM), Na+ also remained unchanged. Left and right hand panel from the same preparation. Glibenclamide added 20 minutes before beginning of trace on the right hand panel. Like in Figure 4, left and right hand panel from the same preparation


Keywords: Arteria coronaria,  Arteria coronaria,  Diagramm,  Efflux,  Efflux,  Glibenclamid,  glibenclamide,  ischaemia,  Ischämie,  Kalium,  potassium

K-Efflux in Koronararterien
Figure 6: Effect of tetramethylpyrazine (a non-sulfonylurea compound known to block K+ATP channels in various tissues, in the literature also named ligustrazine) during simulated ischaemia in an isolated pig coronary artery preparation. Tetramethylpyrazine reduces rate and extent of K+-efflux from the tissue. Left and right hand panel from the same preparation. Tetramethylpyrazine added 20 min before beginning of trace on the right hand panel. Gap represents 30 min.


Keywords: Arteria coronaria,  Arteria coronaria,  Diagramm,  Efflux,  Efflux,  ischaemia,  Ischämie,  Kalium,  potassium,  tetramethylpyrazin,  tetramethylpyrazin

K-Efflux in Koronararterien
Figure 7: Ischaemia induced K+ accumulation in 6 isolated pig coronary artery strips in the presence (closed symbols) and absence (open symbols) of glibenclamide (50 microM). Data from experiments similar to those in Figures 4 and 6.


Keywords: Arteria coronaria,  Arteria coronaria,  Diagramm,  Efflux,  Efflux,  Glibenclamid,  glibenclamide,  ischaemia,  Ischämie,  Kalium,  potassium

K-Efflux in Koronararterien
Figure 8A-B: A. Lack of effect of alpha-cyano-4-hydroxycinnamate (cinnamate, a lactate transport inhibitor) on ischaemia induced K+ efflux in an isolated pig coronary artery strip. Preparation has been incubated with 4 mM cinnamate for 15 minutes before beginning of trace in right hand panel. Left and right hand panel from the same preparation. Gap represents 20 min. B. In Cl-- free solution (Cl- replaced by glucuronate one hour before testing the effect of simulated ischaemia) rate and extent of K+ accumulation are the same as in the presence of Cl-. Gap represents 60 min. Left and right hand panel from the same preparation (like in A).


Keywords: Arteria coronaria,  Arteria coronaria,  Cinnamat,  cinnamate,  Diagramm,  Efflux,  Efflux,  ischaemia,  Ischämie,  Kalium,  potassium

K-Efflux in Koronararterien
Figure 9: Glibenclamide partially inhibits ischaemia induced K+-efflux in an isolated pig coronary artery strip. Left and right hand panel from the same preparation. Glibenclamide added 20 minutes before beginning of trace on the right hand panel. Gap in trace represents 30 minutes. The addition of 1 mM Ba2+ does not inhibit the glibenclamide-insensitive component of ischaemia induced K+ efflux


Keywords: Arteria coronaria,  Arteria coronaria,  Diagramm,  Efflux,  Efflux,  Glibenclamid,  glibenclamide,  ischaemia,  Ischämie,  Kalium,  potassium