1- or 3-mg capsules, PO

Mast cells were removed from 250-gram rats by peritoneal lavage with 15 ml of Hank’s BSS containing 50 units/ml of heparin USP. The cells were washed twice in the above buffer by centrifugation at 750 g for 10 min and resuspended in Tyrode’s buffer, pH 7.4, containing 2°/o heat-inactivated normal rat scrum. These cells were then layered and centrifuged 150 g for 15 min on Ficoll gradients prepared by gradients of 4 ml of 30% Ficoll over 2 ml of 40% Ficoll. The Ficoll was made up in Tyrode’s buffer, pH 7.4. The cells were again washed twice in Tyrode’s buffer and rat serum to remove the Ficoll. 2-4 X 10^5 cells/ml mast cells were then incubated with the drugs before addition of compound 48/80, 0.2 mkg/ml (Burroughs-Welcome, Tuckahoe, N.Y.) after which they were placed in a 37 °C bath for 5 min. The cells were spun out at 750 g for 10 min and the supernatant made 0.4 N with respect to HC104. After an additional spin, the histamine released into the supernatant was assayed by an automated Technicon modification of the fluorimetric assay. 10 mkCi 45CaCI2 was added to 1-2 X 10^7 cells suspended in 5.0 ml of Tyrode’s buffer. When U-42,585E (LODOXAMIDE ETHYL) was present, it was added immediately before addition of the ionophore. The ionophore (A23,187) was made up in 100% DMSO at 10 mg/ml and diluted out to an appropriate concentration in Tyrode's buffer.