Blood, liver and lung kinetics of technetium-99m-labelled granulocytes in the rat. Study by external monitoring with a gamma camera.

The external counting method was used to simultaneously measure the kinetics of intravenously injected polymorphonuclear cells labelled with Technetium 99m, in the lungs, liver and blood of rats. When radiolabelled polymorphonuclear leukocytes (PMN) are injected into animals, a large part is taken up by the various organs. This uptake may result from intravascular aggregation, capillary blocking (in which case the transit of the PMN is slowed down), vascular margination or, finally, from tissue infiltration. A rapid increase in PMN was observed initially in the lungs (first seconds), followed by a progressive decrease (t1/2 = 50 min). At the same time, PMN in the liver increased and that in the blood slowly decreased. The kinetics of distribution in the lungs, liver and blood were not modified when the PMN were injected through the aorta, via a carotid catheter, instead of intravenously. Since there was no shunt, vascular resistance was not the cause of the slow transit of PMN through the organs, and we favour the hypothesis that vascular margination of PMN is responsible for their kinetics. When heat damaged PMN were injected, the kinetics of their distribution in the lung, liver and in the blood were clearly altered.