Brief Reports

Vox Sang. 14: 224-227 (1968)

The Survival Rate of Irradiated Rats After Treatment with Platelet Lipid Extracts Alone and in Combination

with an Antifibrinolytic Agent

P. DE NICOLA, E. F. LUSCHER, M. COPPI and G. MONTANARO

Clinica Medica and Cattedra di Gerontologia, University of Pavia, and Theodor Kocher Institute, University of Berne

In previous investigations [2,3], carried out on normal and irradiated rats, the effects of platelet extracts on the bleeding time and -inten- sity, the prothrombin time and the fibrinolytic activity have been studied. The most favorable effects were obtained with lipid extracts from platelets alone or in combination with an antifibrinolytic agent (Trasylol@). These results incited a study on the survival rates of irradiated rats under the same experimental conditions. The present paper summarizes the data obtained in a larger series of experiments, in which the survival rates of irradiated, treated and untreated rats were compared.

Material and Methods

Two-hundred albino rats, the average weight of which was about 250 g, were used.

The following technique of partial irradiation was practiced : 10 mA, skin distance 30 cm; filter 2 Al.: 100 r/min. On the first day 1000 r (120 Kv) were administered, followed by 200 r on the 6th and 8th day (220 Kv).

Platelet lipid extract was prepared according to the technique des- cribed in detail elsewhere [2, 31: Washed human platelets were sub- mitted t o mechanical homogenization for 8 min. a t 13700 rpm. After centrifugation for 30 min at 1500 g, the sediment was lyophilized

These investigations have been carried out as a cooperative study and with the support of grants SA. 5-2-05 I3 ( 1 1 1 ) SA. 5-2-05/916 (65) from NATO, assigned to Prof. P. Introzzi, Director of the Clinica Medica, University of Pavia.

DE NICOLA et 01. 225

and the lipids were extracted with a 2 : 1 (v/v) mixture of chloroform- methanol. After evaporation of the solvents and drying (7OoC), the residue was dissolved in ethanol. Ten volumes of water and 190 volumes of acetone were then added. From the dried precipitate, which essentially contained phospholipids, a 1% emulsion in a 3% isotonic albumine solution was prepared. This extract (platelet extract L) was administered intravenously at the daily dose of 0.2 ml for 6 days.

The parotid inhibitor (TrasylolB), Bayer, Leverkusen) was used as an antifibrinolytic agent a t the daily dose of 10 units; it was ad- ministered intravenously for 6 days.

The treatment with platelet lipids alone, or in association with the antifibrinolytic agent was started three days after the last irradiation, when the platelet count had reached a value of about 40000 plate- lets/mm3.

Platelets were counted by means of the direct method, using the Sequestrene-Brilliant-Cresylblue technique, as described by DE NI- COLA [l].

Results

Figure 1 summarizes the obtained results. The survival rate of irra- diated, treated rats was higher than the one of irradiated, untreated animals. When platelet lipids alone were used, fourteen rats of the treated group were still alive a t the time when all of the untreated group were dead. A still greater number of the animals survived when platelet lipids were administered in combination with the antifibrinol- ytic agent Trasylo1.B

This difference became highly significant only in the period which followed the treatment. With the combination of both agents, the 19 surviving rats remained alive for more than 14 days after the death of all the untreated animals. It should be noted that in this parti- cular experiment the onset of the treatment was delayed as compared to the series with lipids alone. This was due to a slower development of the thrombocytopenia which might reflect differences in the irra- diation procedure; however, within one experiment, conditions were strictly comparable. It might well be that the survival rates of the treated rats would still improve with an earlier start of the administra- tion of the combination of lipids and inhibitor.

226 DE NICOLA et al. The Survival Rate of Irradiated Rats

I I I I I I l l I I 0 10 20 30 40 50 0 10 20 30

Dayr

Fig. 1. Survival curves of irradiated rats, treated with platelet lipids in combination with the fibrinolytic inhibitor Trasylol @ (left side), and with platelet lipids alone (right side). Curves designated with B represent the survival rates of untreated, irradiated controls.

Conclusions

The work of SALMON [4] on the bleeding tendency in thrombocyto- penic animals suggests that the unbalance of the hemostatic and fibrinolytic systems is responsible a t least in part for the typical symptoms of the irradiation syndrome. This assumption is furthermore supported by our earlier investigations on the bleeding time and -intensity, the prothrombin consumption, and the fibrinolytic activ- ity in irradiated rats [2, 31.

The data reported here demonstrate the protective action of platelet lipid extracts on the hemorrhagic irradiation syndrome in the rat. It remains to be elucidated whether this effect is entirely due t o the suppression of the hemorrhagic manifestations or whether other, hitherto unknown components are equally influenced. The combination of platelet extracts and of an antifibrinolytic agent finally, proved t o be even more effective. In fact, under the chosen experimental conditions, this combined treatment had the most pro- nounced effect on the survival rate of irradiated rats; it proved more effective than any other approach to the problem of the therapy of the irradiation syndrome by means of stable platelet derivatives.

After Treatment with Platelet Lipid Extracts Alone.. . 227

References

1. DE NICOLA, P.: The laboratory diagnosis of coagulation defects (Charles C Thomas, Springfield, Ill., 1955).

2. DE NICOLA, P.; LUSCIIER, E. F.; GIBELLI, A.; SOARDI, F. and CIPOLLI, P. L. : Modifications of the bleeding time and intensity, of prothrombin consumption and of fibrinolysis in rats after administration of platelet extracts alone and with antifibrinolytic agents. I1 Farmaco (ed. scient.) 22: 627 (1967).

3. DE NICOLA, P.; LUSCHER, E. F.; GIBELLI, A.; SOARDI, F. and CIPOLLI, P. L.: Effects of platelet extracts alone and in combination with antifibrinolytic agents on bleeding time and intensity, on prothrombin consumption, and fibrinolysis in irradiated rats (to be published).

4. SALMON, J. : Inhibition du purpura thrombopBnique immunologique par l’acide epsilon-aminocaproPque. Thromb. Diath. haemorrh. 6: 172 (1961).

Authors’ addresses: Dr. P. de Nicola, Cattedra di Gerontologia, Dr. M. Coppi and Dr. G. Montanaro, Clinica Medica, University of Pavia, Pavia (Italy); Dr. E. F. Liischer, Theodor Kocher Institute, University of Berne, Berm (Switzerland).