Collagenase-induced thrombocytopenia

Male Sprague-Dawley rats weighing 260-300 g are used. The animals receive the test compound or the vehicle (controls) by oral, intraperitoneal or intravenous administration. After the end of the absorption time (i.p. 30 min, p.o. 60 min, i.v. variable), rats are anesthetized with pentobarbital sodium (i.p.). One carotid artery is cannulated for blood withdrawal and one jugular vein is cannulated for inducer injection. The animals receive an intravenous injection of heparin and 20 min later, approx. 100 il blood are collected (initial value). Ten min later, the thrombocytopenia-inducing substance collagenase is administered intravenously. 

At times 5,10,20 and 30 min following the injection of collagenase, samples of approx. 100 xl blood are collected into potassium-EDTA-coated tubes. The number of platelets is determined in 10 il samples of whole blood within 1 h after blood withdrawal using a microcellcounter. See Volkl and Dierichs (1986) for details. 

The percentage of platelets is determined in vehicle control and dosage groups at the different times following injection of collagenase relative to the initial value of control or dosage group, respectively. Calculated percent values of controls are set at 100 %. 

Percent inhibition of thrombocytopenia is calculated in dosage groups relative to controls. 

Statistical significance is evaluated by means of the unpaired Student s t-test. 

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