Sustained Bleeding after a leech Bite in the Apparent Absence of Hirudin

Summary

The bite of the medicinal leech bleeds for many hours. For decades it has been assumed that the remarkably prolonged bleeding time of a leech bite wound is due to hirudin, a specific anti-thrombin secreted by the leech during feeding. By measuring haematological parameters of blood oozing from a leech bite wound on 15 different occasions in 7 human volunteers, we demonstrate that the hirudin-sensitive coagulation parameters, including thrombin-induced platelet aggregation, are prolonged for only 15 min, after which they return to normal. This suggests that excess hirudin secreted by the leech is washed out during this period. However, bleeding from the leech bite wound persists for a mean of 10 h. Platelets in smears of exuding blood show no evidence of spontaneous aggregation, but in vitro platelet aggregation can be induced by exogenous collagen at any time. In view of sustained bleeding in the apparent absence of hirudin, attention is focussed onto an unsuspected factor or factors which may better explain the prolonged bleeding phenomenon.

Keywords

Medicinal leech - Hirudin - Bleeding time - Radioimmunoassay - Platelet function

• References

• 1 Haycraft JB. On the action of a secretion obtained from the medicinal leech on the coagulation of blood. Proc R Soc London 1884; 36: 478-487
• 2 Markwardt F. Die Isolierung und chemische Charakterisierung des Hirudins. Z Physiol Chem 1957; 308: 147-156
• 3 Walsmann P, Markwardt F. On the isolation of the thrombin inhibitor hirudin. Thromb Res 1985; 40: 563-569
• 4 Harvey RP, Degryse E, Stefani L, Schamber F, Cazenave JP, Courtney M, Tolstoshev P, Lecocq JP. Cloning and expression of a cDNA coding for the anticoagulant hirudin from the bloodsucking leech, Hirudo medicinalis. Proc Natl Acad Sci USA 1986; 83: 1084-1088
• 5 Sawyer RT. In: “Leech Biology and Behaviour” Vol II, Feeding, Ecology and Systematics. Oxford University Press; Oxford: 1986. pp 496-501
• 6 Lent CM. New medical and scientific uses of the leech. Nature 1986; 323: 494
• 7 Rao P, Bailie FB, Bailey BN. Leechmania in Microsurgery. Practitioner 1985; 229: 901-904
• 8 Mielke CH, Kaneshiro MM, Mahler IA, Weiner JM, Rapaport SI. The standardized Ivy bleeding time and its prolongation by aspirin. Blood 1969; 34: 204-215
• 9 Dale HH, Laidlaw PP. A simple coagulometer. J Pathol Bact 1911; 16: 351
• 10 The Instruction Manual for the Whole Blood Aggro-Meter, Models 500, 530, 540, 550, 560 Issue C. 07/1985 Appendix 2. pp 1-28
• 11 Tam SW, Fenton JW, Detwiler TC. Dissociation of thrombin from platelets by hirudin. J Biol Chem 1979; 254: 8723-8725
• 12 Rigbi M, Levy H, Iraqui F, Teitelbaum M, Orevi M, Alajoutsijarvi A, Horovitz A, Galun R. The saliva of the medicinal leech Hirudo medicinalis – I. Biochemical characterization of the high molecular weight fraction. Comp Biochem Physiol 1987; 87 B 567-573
• 13 Markwardt F. The comeback of hirudin. An old established anticoagulant agent Folia Haematol (Leipzig) 1988; 115: 10-23