In experimental animals, intravenous injection of ADP produces platelet accumulation in the lungs, together with thrombocytopenia. Since platelets can be isotopically labelled without gross functional disturbance, we have sought to develop a method for measurement of aggregation and disaggregation of labelled platelets in vivo.Guinea-pig platelets are labelled with Indium-111 and injected into narcotised animals (Sagital, 37 mg/kg). Two collimated crystal scintillation probes are used to monitor the thoracic region (heart and lung) (Cl) and the vascular compartment (hind limbs) (C2). An indwelling cannula (25 SWG) is inserted into a foot vein and kept patent by small volumes of heparin (100 u/ml). Intravenous ADP (10 mg/kg) causes transient accumulation of platelets within the lung, as well as thrombocytopenia, within a two minute period. During a response, counts are monitored from both probes and retained in a dedicated microcomputer, so as to permit rapid display of results in tabular and graphical form. Usually, ninety consecutive 4 sec. counts are recorded, results being expressed both as a paired difference (C1-C2) and as a ratio (C1/C2). Repeated challenge can be made with ADP and a dose-related response is obtained over the range 10-30 mg/kg. Treatment with sulphinpyrazone or prostacyclin inhibits aggregation.
Imaging of β-amyloid plaques by near infrared fluorescent tracers: a new frontier for chemical neuroscience
