[Studies on the thrombocytopoietic factor. I. Elaboration of investigative methods].

The authors present a method of determination of the activity of the thrombocytopoietic factor (AT) by means of biological test on rats using 75-Se-selenomethionine for in vivo labelling of platelets. For suppression of endogenous thrombocytopoiesis the rats received antiplatelet rabbit serum which was used for investigations in the period of reactive hyperthrombocytosis. The thrombocytopoietic activity was expressed in radioactivity impulses per 1 mg of platelet protein of rats which permitted to eliminate the error-fraught determination of platelet count. A statistically significant rise in the thrombocytopoietic activity was demonstrated in rabbits with experimental thrombocytopenia as compared with the AT in healthy rabbits. The error of the method was 9.6-9.8 percent (P less than 0.05).