MÉTODOS DE ANÁLISIS

0 .5 -5 m g /k g Adrenaline 0 .4 Adrenaline 0 .8 Adrenaline 1 .6 1 1 5 0 1 3 8 2 0 7 • 1 9 9 2 1 7 2 1 6 8 1 5 0 1 4 8 1 7 6 3 1 9 2 1 8 6 1 8 6 1 7 6 1 6 4 4 1 6 4 1 6 4 1 6 0 151 1 61 5 1 7 2 1 7 3 1 7 4 1 5 5 1 7 0 6 1 7 2 1 7 3 1 6 3 1 4 8 1 4 2 7 1 5 3 1 5 6 1 4 3 1 4 3 - - 8 2 1 0 2 1 6 - - 1 8 8 2 0 4 M ean 1 7 3 1 7 2 1 6 9 1 5 8 1 7 3 ± SD ± 2 0 ± 2 3 ± 2 2 ±1 7 ± 2 2 p value vs. - NS NS < 0 .0 5 NS last state

KEY: Adrenaline dosage in ^ig.kg i .min*^.

-- denotes stage of investigation omitted in individual dog.

The response of individual animals to alterations in adrenaline and trim etazidine doses was also studied and limited dose- response curves constructed. These data were derived from the study itself, or from additional procedures (over and above those described in the original protocol) which were carried out on the experimental preparation before humane killing. In two animals, the adrenaline infusion rate was further increased from 1.6 to 4.0 pg.kg \m in \ Owing to the numbers responding to low doses of trimetazidine and the relative resistance to adrenaline infusion shown (Table 4.2, Figure 4.2), data sets from individual dogs will

be shown. In any case the group response to adrenaline has been well shown at each stage in Table 4.2.

Limited dose-response curves were constructed between the dose of adrenaline and the slope of the cyclic flow reductions. Figure 4.3 demonstrates such a dose-response curve in Experiment No. 6. The cyclic flow reductions increased until a maximum response was reached. 30 Slope of cyclic flo v reductions 20 - ( m l/m in /m in ) 0 1 2 3 4 5

Adrenaline infusion rate ( lig /k g /m in )

F IG U R E 4.3: Effect of increasing adrenaline concentration on slope of cyclic flow reductions. Data from Experiment 6. Tfie measured cyclic flow reductions just before and during adrenaline infusions are sfiown. Tfie double point at adrenaline infusion rate of 0.4pg.kg'^ .min'^ is after return to that level from the higher infusion rates. Total dose of trim etazidine given beforehand was Smg.kg’ T It can be seen that the maximum adrenaline effect has been closely approached.

In other dogs (numbers 2 and 4 in the experimental series) a similar increase in the slope of cyclic flow reductions was demonstrated. These are shown in Figures 4.4 and 4.5. In these experiments, the maximum response does not appear to have been reached, despite the very high rate of rethrombosis seen in

Experiment 4 (Figure 4.5), 20 Slope of cyclic flo v reductions ( m l/m in /m in ) 0 -c> 0 1 2

Adrenaline infusion rate ( iig /k g /m in )

F IG U R E 4 .4 : Increase of intracoronary thrombosis rate by adrenaline. Data, from Experiment 2, which demonstrate the effects of increasing adrenaline concentration on the slopes of cyclic flow reductions.

40 Slope of cyclic flo v reductions ( m l/m in /m in ) 20 10 0 1

Adrenaline infusion rate ( jig /k g /m in )

F IG U R E 4 .5 : Enhancem ent of cyclic flow reductions (thrombosis rate) by increasing adrenaline concentration. The findings from Experiment 4 are similar to those in Figure 4.4, but are less than the maximum response shown in Figure 4 .3 .

In the remaining dogs, as can be seen from Table 4.2, cyclic flow reduction slopes were re-established or increased significantly by adrenaline infusion. It can also be seen that experiments 1, 3, 5, 7 and 8 present too few data points for illustrations.

Another approach is to keep the adrenaline infusion constant at a high rate (I.Gpg.kg'Tmin'^); the dose of trimetazidine can then be increased. Data from the same dog (No 4) are shown in Figure 4.6:

40 Slope of c yclic flo v reductions 30 - ( m l/m ln /m ln ) 20 - 2 3 4

Cum ulative dose of trim e ta z id in e (m g /k g )

FIGURE 4.6: Additional trimetazidine during high dose adrenaline infusion. Further data from experiment 4. This demonstrates effects of increasing the cumulative dose of trimetazidine, in one dog, while an adrenaline infusion was continued at 1 .Gpg.kg'^ .m in '^ . The slope of the cyclic flow reductions decreases thus indicating continued activity of trimetazidine.

The response demonstrates continuing activity of trimetazidine at higher dosage. The drug is therefore capable of overcoming the effects of considerable stimulation of the platelet a g- adrenoreceptor.

S e r ie s ( il) : Coagulation studies and bleeding tim es

The coagulation variables are shown in Table 4.7. Baseline values are comparable to our own laboratory normal values for dogs. There were no significant effects on prothrombin time, thrombin time, partial thromboplastin time or fibrinogen level, either due to trimetazidine administration, or with the addition of aspirin. Bleeding time at baseline was normal for our laboratory and close to a published value for dogs (2.62±0.49 mins) [Jergens et al., 1987]. Thirty minutes after trim etazidine administration, there was significant shortening of bleeding time (p < 0 .0 5 ). Thirty minutes after intravenous aspirin at 5 mg.kg \ bleeding time was significantly prolonged and this effect was more pronounced by sixty minutes.

As bleeding time is measured to the nearest half minute, there is a potential inaccuracy of one minute. If this is taken into account for com parisons betw een the s e p a ra te stag es of the investigation, the following corrections can be made:

first, if 1 minute is added to the bleeding time values at 30 and 60 minutes after trim etazidine, no significant difference from control is seen. Second, despite this 'corrected' value, aspirin at 60 minutes still caused a significantly (p<0.05) longer bleeding time than that seen following trimetazidine administration.

Table 4.7 Effects of trim etazidine ± aspirin on bleeding time and coaguiation

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