Abstract
Summary
Following the intravenous administration of [35S]heparin in the dog, a direct relationship between plasma 35S activity and anticoagulant activity was observed suggesting that the radiolabel remained part of the intact heparin molecule.
An initial rapid loss of [35S]heparin from the intravascular compartment was observed. This was due to a rapid extravascular distribution and renal excretion.
The quantity of 35S radiolabel excreted into the urine during the first hour accounted for as much as 25% of the dose administered. There appeared to be no correlation between the amount of [35S]heparin infused and urine excretion rate.
Extravascular retention of the radiolabel was variable but substantial in all animals, averaging 60% of the dose.
The retained radiolabel in necropsy tissues showed widely ranging concentrations. The highest amounts were consistently found in the liver. The lowest amounts were consistently found in the brain. No remarkable differences were found between animals receiving a single dose of heparin or additional heparin by infusion. Five arbitrary categories of concentration were distinguished and the tissues were classified accordingly.
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