On the in Vivo Clearance of Thrombin^[*]

Summary

The turnover of labeled bovine thrombin was studied in heparinized dogs. The results of these studies indicate that

1. thrombin is rapidly removed from the blood, clearance takes place predominantly by the liver ;

2. the uptake occurs by the Kupffer cells ;

3. after its uptake the thrombin is rapidly broken down ;

4. in the absence of the liver thrombin is slowly cleared by extrahepatic phagocytes ;

5. the rate of thrombin clearance is so rapid and its critical dose so small that this protein can be used to study hepatic blood flow and Kupffer cell clearance function.

^* The first part of this paper was presented at the Sixteenth Symposium on Blood, January 19-20, 1968, Detroit; the second part at the Fifth National Scientific Meeting of the Reticuloendothelial Society, New York, December 1—4, 1968.

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