Summary
The effect of the radioisotope P32, hydrolysed dextran, reserpine, stypturon on thrombus formation was determined by injecting these substances into rats before a standardized operation on the jugular vein. 5 hours after the operation 65% of control animals showed a thrombus. 10 days after intravenous injection of 2, 3, or 4 µC/g, the incidence of thrombosis was lowered in direct relation with the reduced platelet counts varying from 65% incidence for counts above 200 000/mm3 to 0% incidence for counts less than 38 000/mm3. Animals injected with dextran, 2 hours, or reserpine, 48 hours before the operation had an incidence of thrombosis of 48% (P <0.01). The incidence of thrombosis was not significantly lowered by mecholyl, producing a hypotension similar to that after dextran, nor by stypturon. The importance of the method for the quantitative evaluation of substances having an effect on thrombus formation is emphasized.
