Leukotriene D4-induced homologous desensitization of calcium mobilization in rat basophilic leukemia cells.

Previous work from our laboratory demonstrated that RBL-1 cells express membrane receptors for leukotriene (LT)D4 and that agonist stimulation of these receptors results in mobilization of intracellular calcium ([Ca++]i). We have used this LTD4 receptor-mediated event to examine the effects of homologous desensitization in RBL-1 cells. Prior exposure of RBL-1 cells to LTD4 resulted in a 40% reduction in the amount of maximal [Ca++]i mobilization. This desensitization was concentration- and time-dependent, with an EC50 of 1 to 3 nM and with 50% of the desensitization occurring after 7.5 min of pretreatment. SKF 104353 (100 nM), a high affinity, LTD4-receptor antagonist, blocked completely LTD4-induced desensitization of RBL-1 cells. The LTD4-induced desensitization was stereospecific, as the (5R,6S)-enantiomer of LTD4 was at least 100 times less potent than LTD4. Pretreatment of RBL-1 cells with LTD4 did not alter the ability of thrombin or ATP to induce [Ca++]i mobilization, suggesting that the desensitization was of the "homologous" type. The density of [3H]LTD4 receptors in RBL-1 cell membranes was decreased 23% by prior treatment of RBL-1 cells with LTD4. These results demonstrate that the [Ca++]i mobilization induced by LTD4 can be desensitized as a result of prior exposure to LTD4 and that the LTD4 receptor and/or second messenger systems can be specifically down-regulated.