Abstract
Antigen, anti-IgE and concanavalin A (Con A) induced an increase in both the incorporation of the 3H-methyl moiety into phospholipids and histamine release. Maximal incorporation of the 3H-methyl moiety into the lipid fraction of the cells was observed within 15 sec and 1 min after being challenged with antigen (100 μg/mL) and anti-IgE (200 μg/mL) respectively. However, the methylated phospholipid decreased rapidly. The addition of Con A (10 μg/mL) also increased phospholipid methylation, which reached a maximum at 5 min after challenge. Trans-4-guanidinomethylcyclohex-anecarboxylic acid p- tert-butylphenyl ester hydrochloride (NCO-650; 27 μM) strongly inhibited the incorporation of the 3H-methyl moiety into phospholipid by antigen, anti-IgE and Con A. The ic 50 values of NCO-650 for phospholipid methylation in response to antigen, anti-IgE and Con A were 1.5, 4.7 and 1.1 μM respectively. Although the Ca 2+-ionophore A23187 did not induce phospholipid methylation, it caused histamine release.
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