Migration of polymorphonuclear neutrophils and macrophages from bone marrow to the peritoneal cavity after (3H)-thymidine labelling of rat tibial bone marrow in vivo.

The kinetics of migration of bone marrow cells to the peritoneal cavity have been studied using in vivo labelling of the marrow of the rat tibia with (methyl-3H)-thymidine (TdR). The incorporation of 3H into DNA is directly related to the amount infused over a thirty-minute period, though only 2-3% of the infused dose is incorporated into DNA in the bone. Autoradiography has shown widespread labelling of bone marrow cells throughout the tibia. Band cells and polymorphonuclear neutrophils (PMN) show an increase in labelling during the 2-3 days after infusion, confirming the maturation of granulocytes prior to their release to the circulation. The disappearance of 3H-labelled DNA from the bone occurs rapidly during the 3 days after infusion of TdR with a half-life (t1/2) of 1.4-1.7 days. There is a concomitant increase in the specific activity of DNA in peritoneal cells elicited by agar, particularly in the macrophage (M phi). Labelling of PMN in the peritoneal exudate occurs only when agar is injected from 2-4 days after infusion of TdR. The time for maturation of PMN in the rat bone marrow (BM) (2-3 days) has been confirmed, and the method of labelling permits both measurement of the migration of cells from BM to peritoneal cavity and an estimate of the rates of migration.