A minimally invasive technique for the study of intravascular platelet aggregation in anesthetized rats

A method for monitoring platelet aggregation in vivo in the rat is described, using platelets labeled with indium3+ oxine and recording the increase in radioactivity count in the lung after injection of adenosine diphosphate and collagen. The effects of adenosine diphosphate and collagen are reproducible between animals. 5-Hydroxytryptamine creatine sulfate, which is inactive on rat platelets in vitro, causes aggregation in vivo, and adrenaline, which is proaggregatory in vitro inhibits adenosine diphosphate-induced aggregation in vivo. Female rats are relatively insensitive to the aggregating agents, particularly during proestrus, although when platelets from proestrus females were injected into male rats, their sensitivity was increased. Platelets from male rats injected into female rats in proestrus have low sensitivity.