Hirudin

HIRUDIN (from Latin hirudo-leech), a substance contained in the head glands of medicinal leeches (h. medicinalis), that prevents blood clotting. Discovered in 1884 by Haycraft; the name "hirudin" was proposed by Jacobi, in whose laboratory the first preparations of hirudin were obtained. In pure form, hirudin has not yet been isolated; the preparations obtained give protein reactions (albumoses). H. is not toxic—rabbits tolerate intravenously up to 60 mg per 1 kg of weight without any consequences; the anticoagulant action of H. persists even after boiling its solutions. H. is used in physiological experiments, to prevent blood clotting (e.g., when working on isolated organs). It is sold in the form of a dry preparation of relatively high activity—1 mg prevents clotting of up to 20 cubic cm of rabbit blood. Due to the high cost of H. on the market, "novirudin" was proposed, which is a salt of melanic acid; however, the latter is apparently significantly more toxic, and its action is less reliable. For work, one can use simply an extract from leech heads: the severed heads are triturated with sand and extracted with physiological solution (1 cubic cm per head). To prevent the animal's blood from clotting, it is sufficient to inject 3 cubic cm of such extract per 1 kg of the animal's weight.