Mast-Cell Heterogeneity: Functional Comparison of Purified Mouse Cutaneous and Peritoneal Mast Cells

To investigate the functional heterogeneity of mouse mast cells, we extracted and purified cutaneous and peritoneal mast cells from 10- to 18-week-old BALB/c mice and compared their responses to secretagogues. Cutaneous mast cells (CMC) were extracted from mouse ears after digestion with hyaluronidase and collagenase in MEM containing 25% fetal calf serum and purified on a discontinuous Percoll gradient. The histamine content of cells obtained from the 30/40% interface was 1.0 ± 0.1 pg/cell (mean ± SE), with a mast- cell purity of 68.6 ± 4.4% and a viability of >93%. Peritoneal mast cells (PMC) were obtained by lavage with modified Tyrode's buffer followed by purification on 22.5% and 3-9% metrizamide gradients. The histamine content of cells was 12.2 ± 0.8 pg/cell, with a mast-cell purity of 95.9 ± 0.6% and a viability of > 95%. Histamine release induced by A23187 from CMC peaked at 3.0 μM A23187 (19.1 ± 4.2%), at 3.0 min (22.3 ± 2.3%), and at 30°C (17.6 ± 2.6%). In contrast, histamine release from PMC peaked at 8.0 μM of A23187 (49.4 ± 12.1%) and at 15.0 min (48.5 ± t2.2%). Release of histamine from PMC was observed at all the temperatures tested from 22 to 45°C. Histamine released from CMC and PMC induced by A23187 was calcium dependent. Histamine release induced by compound 48/80 from CMC peaked at 0.5 μg/ml of compound 48/80 (23.0 ± 7.4%) and at 5.0 min. incubation (16.3 ± 2.0%) whereas release from PMC peaked at 10.0 μg/ml (31.9 ± 2.6%); release from PMC was similar at all the time points examined (1 -15 min). Histamine release induced by substance P (SP) from both CMC and PMC peaked at 5.0 μM (18.8 ± 6.6% and 12.6 ± 3.7%, respectively); however, the maximal release from CMC occurred at 3.0 min (18.2 ± 3.2%) and from PMC at 30.0 min (11.4 ± 2.0%). SP-induced histamine release from CMC was calcium dependent, whereas release from PMC was only partially inhibited by EDTA. This study demonstrated that functional heterogeneity exists between these two populations of mast cells