The influence of heparin on the in vivo distribution of IN-111 labeled platelets

We investigated the influence of heparin (H) (bolus i.v.; 100-200 I.U./kg.) on the in vivo distribution and accumulation of autologous indium-111-platelets (In-111-P) on experimental pulmonary emboli (PE) in a canine model. Using a thrombin clot formation technique, we induced pulmonary emboli in ten dogs; three dogs were treated with heparin (H), and seven were not (NH). Of five control animals without PE, two were heparinized (H-control) and three were not (NH-control). Animals were sacrificed after 4 to 5 hours of serial blood sampling and sequential scintigrapy. We observed that heparin increased the recovery of In-111-P in the peripheral blood circulation of both control and PE dogs, and reduced the liver uptake of In-111-P in the PE dogs. No PE could be detected while the dogs were fully heparinized, but as the heparin effect dissipated over time, the deposition of In-111-P permitted the scintigraphic detection of PE.