Class III agents are pharmacologically heterogeneous, varying in their selectivity for different potassium currents . Therefore, the aim of the present study was to compare cardiac electrophysiological effects of the two class III antiarrhythmic agents tedisamil and D-sotalol in isolated guinea pig hearts perfused by the method of Langendorff.
Design: Eighteen white guinea pigs of either sex, weighing 200 to 300 g, given food ad libitum, were divided into two groups of nine animals each. In the first group the effects of tedisamil on the cardiac conduction system, sinus rate and refractoriness were evaluated. In the second group of experiments with the same protocol, the effects of D-sotalol were determined. The results were obtained from 15 of 18 preparations studied.
Experimental protocol: Guinea pigs were injected intraperi-toneally with 250 U of heparin 1 h before being killed by dislocation of the neck. The chest was quickly opened, and the heart was removed and attached to a modified nonrecirculating Langendorff perfusion system (Anton Pear, Graz, Austria). All procedures met the guidelines set by the Committee on Animal Care at the authors’ medical centre. Ty-rode’s solution, saturated with a mixture of oxygen (95%) and carbon dioxide (5%) and warmed to 36°C was used as perfusate (in mM: NaCl 132.1, KCl 2.7, CaCl2 2.5, MgCl2 1.15, NaHCO3 24.0, NaH2PO4 0.42 and D-glucose 11). Immediately after the heart had been attached to the Langendorff perfusion system, electrocardiographic (ECG) recordings were taken from the epicardial surface. The perfusion rate was progressively increased until it reached 8 mL/min or a perfusion pressure of 60 cm H2O so that atrioventricular (AV) conduction, a sensitive parameter for acute ischemia in this preparation, was less than 65 ms and the spontaneous sinus rate was about 200 beats/min. Each heart was allowed to equilibrate for 30 mins. If rhythm irregularities occurred during the equilibration period, the heart was discarded. You can soon shop with a nice pharmacy offering Cheap Asthma Inhalers Online buy here to benefit more.