Figure 3.

Representative microphotographs of postcapillary mesenteric venules of intact rats. Large black dots are used to align the optical Doppler velocimeter used to measure red cell velocity, and are occasionally moved from the vessel center to obtain a better view of the leukocyte–endothelial interface for photographs. Left and center: Photographs were taken before and after 30 minutes of breathing 10% O₂, respectively. Red arrows indicate MCs, and green arrows indicate adherent leukocytes. Hypoxia induces the degranulation of MCs, as shown by the uptake of ruthenium red, and increased adherence of leukocytes to the endothelium. Right: Venule of an intact rat pretreated with the CCR2b receptor antagonist RS-102895 (10 μM, applied topically). This photograph was obtained at 30 minutes of 10% O₂ breathing. In contrast with 30 minutes of breathing 10% O₂, pretreatment with RS-120895 prevented the degranulation of MCs and the leukocyte–endothelial adherence of alveolar hypoxia. Numbers below photographs represent mean ± SE of 5 rats in each group. LEA, leukocyte-endothelial adherence, leukocytes/100 μm, MCDI, mast cell degranulation intensity, arbitrary units. * P < 0.01 versus corresponding normoxic control rats. A complete set of the data for this series of experiments is included in the supplement.