Proliferation kinetics of macrophage subpopulations in a rat experimental pancreatitis model

The kinetics of rat macrophage proliferation in the inflamed pancreas was analysed using a duct-ligation pancreatitis model. We performed a double immunostaining of pancreatic cryosections using a panel of monoclonal antibodies to either macrophage-specific (ED1, ED2) or macrophage-related (CR3 and Ia) antigens in combination with a cell marker of DNA synthesis (5-bromo-2'-deoxyuridine, BrdU). One hour labeling with BrdU revealed each recorded macrophage phenotype to have a very high labeling index (12-28%), peaking on day 2 after induction of pancreatitis. The percentage of each proliferating phenotype also reached 20-40% of the total BrdU+ cells on day 2. The proliferating macrophages consisted of heterogeneous subpopulations including monocyte-like cells and resident macrophages. Their growth occurred in a relatively synchronized fashion, and seemed to be triggered by common proliferative signals.