| Propylene glycol mannate sulfate (PGMS), an oceanic drug, is a new type of low anticoagulant heparinoid with low molecular weight. It is a substitute of the polysaccharide sulfate (PSS) .The reason is that PGMS was obtained on basis of a rather systematic study on the relationship between structure and effects of PSS. PGMS administration has been shown to decrease the viscosity of the blood, to inhibit blood coagulation, to decrease fat in the blood and to improve microcirculation and so on. But up to now, the effects of PGMS on cardiac electrophysiology have not been examined .The effects of PGMS on the ionic mechanisms and contractile force (FC) in isolated guinea pig papillary muscles6were examined using a standard microelectrode technique, recording the action potential (AP) and FC synchronously. Guinea pigs of either sex , weighing 300?0g were supplied by the Experimental Animal Center of Henan. After they were stunned , papillary muscle was taken from the right ventricle and perfused with Tyrode solution at a speed of 10 ml·min-1 aerated with 95%O2+ 5%CO2 at 32 + 0.5 癈 and PH 7.4 . Tyrode solution had the following composition (mmol -L-1): NaCl 134, KC1 4.0, MgCl2 0.5, CaCl2 2.0, NaHCO3 12, NaH2PO4 0.42, Glucose 5.5. Perfusion of Tyrode solution must be fulfilled at steady temperature and steady speed in the experiment.Force of contraction (FC) of the papillary muscle was measured with an isometric force transducer which was connected to the tendinous end of the preparation. Initial length was adjusted to yield an optimal contraction amplitude upon stimulation. Transmembrane action potentials were recorded with conventional glass microelectrodes having a resistance of (10-20M Q ) . The maximal upstroke velocity (Vmax) was obtained by an electronic differentiator. Stimulation parameters were: stimulus duration 1ms, frequency 1 HZ and 1.5 times threshold voltage. After impalement was stabilized for 40 min experiments started, record the result of experiment through photograph.For slow action potentials (SAP), after impalement was stabilized for 40 min , high K+(25mmol·L-1) Tyrode solution was prepared by equitable substitution of KC1 for NaCl , containing isoprenaline (1 μmol·L-1) and 4 μmol·L-1 VitC or BaCl2 (0.2mmol·L-1) to elicit SAP after depolarization of the resting potential and inaction of fast Na+ channels. Stimulation parameters were: stimulus duration 3ms , frequency 0.2 HZ , 3 times threshold voltage . After the recording of control SAP for 30 min, Experiments started. The electric and mechanical signals were displayed on the screen of an oscilloscope and the parameters were measured and photographed with camera. PGMS in this experiment was administered in an accumulative manner , the concentration of these drugs respectively were 10, 30, 100, 300, 1000 mg·L-1, the effect of PGMS for guinea pig papillary muscles was observed . There were seven parameters measured: resting potential (RP) , action potential amplitude (APA) , maximal upstroke Velocity (Vmax) , action potential duration at 30%, 50%, 90% repolarization (APD30, APD50, APD90) and contractile force (FC). Only the results obtained from a single cell throughout the whole experimental period were subjected to analysis with two-way ANOVA through SPSS 10.0. Results:81. Effects of PGMS on fast action potential in guinea pig papillary muscles.PGMS at concentrations of 10-1000mg·L-1 caused a concentration-dependent decreases in the APD30, APD50 and APD90 of FAP , The RP, APA, Vmax were not affected obviously by PGMS at the above concentrations.2. Effects of PGMS on FC in guinea pig papillary muscles.PGMS at lO-TOOOmg -L-1 concentration-dependent decreased the force of contraction in isolated guinea pig papillary muscles and the effects could be reversed by normal Tyrode solution.3. Effects of PGMS on slow action potential induced by isoprenaline.PGMS at 10~1000mg·L-1 concentration-dependent decreased the APA, Vmax, APD30, APD50, APD90 of SAP without affecting theRP .The...
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