ABSTRACT
Usually experiments done on isolated working heart preparation must be completed within 1 h, because of declining of cardiac functions after going beyond that limit reported by many authors. Our experiments on guinea pig showed that the viability time lasted at least 2 h. All measured indices of cardiac performance, namely LVP, dP/dtmax, MASP, HR, CF, AF, CO, LVPW, MVO2 and. working efficiency, remained stable within that period of time, .when PcO2 and PO2 of perfusing solution were adjusted at 4.7~7.3 kPa and over 67 kPa respectively, resulting in stability of pH value in 7.4 or so. Modification of the Krebs solution by devoid of phosphate and addition of pyruvate and EDTA may also be responsible for prolongation of the viability time. After such improvement, the preparation will give sufficient time to study the effect of drugs. Its use will be greatly widened.1 -10 mg/L cobra cardiotoxin increased CO, AF, LVEDP, MASP, LVP, dP/dtmax, decreased CF, and unchanged HR.MVO2 and working efficiency were insignificantly increased. These results obtained from this preparation were in accordance with that from other isolated cardiac preparations.