Hemostatic alterations associated with phenylhydrazine-induced anemia in the rat.

Phenylhydrazine (PHZ) is a hemolytic agent which has been used in the treatment of polycythemia vera. Recent studies performed in our laboratory have indicated that the PHZ-induced anemia is immuno-hemolytic in etiology, and a prolonged bleeding time was present in some of the rats chronically treated with PHZ. The nature of this bleeding tendency was explored in the present experiment. PHZ was administered to rats once a week for a six week period. During this time, the animals were monitored for prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen concentration, and individual coagulation factor levels as well as routine plasma chemistries and blood cell counts. In addition, radioimmunoassays (RIA) for prostacyclin, a platelet aggregation inhibitor, and prostaglandin (PG) E2 were performed. PHZ-treated animals displayed a significant elevation in both PT and APTT when compared with saline injected controls, although plasma fibrinogen levels were not appreciably altered. Further tests revealed a PHZ-induced decrease in prothrombin and factor V levels. In addition, a significant increase in plasma serum glutamate oxaloacetate transaminase (SGOT), lactate dehydrogenase (LDH), and alkaline phosphatase levels was observed as well as a diminution in cholesterol and triglycerides following PHZ administration. PHZ treatment also induced an elevation in prostacyclin levels and transient thrombocytopenia. These findings indicate that several factors may contribute to the prolonged bleeding time in PHZ-treated rats including a drug induced thrombocytopenia possibly associated with enhanced synthesis of autologous immunoglobulin G (IgG) against the senescent red cell antigen, and diminished synthesis of vitamin K-dependent coagulation factors which may be mediated by reduced vitamin K uptake by the hypo-cholesterolemic subjects.