The release of luteinizing hormone-releasing hormone (LH-RH), somatostatin (SRIF) and growth releasing factor (GRF) by male rat median eminences (MEs) incubated in vitro for 30 min, in the presence of leukotrienes (LT) C4, D4, E4 and B4 was estimated by radioimmunoassay (RIA). Leukotrienes, with the exception of LTE4 stimulated the release of LH-RH. The dose-response curve was bimodal for LTC4 with two maxima at 10(-8) and 10(-16) M (X2.2 and 1.9, respectively), biphasic for LTD4 with a maximum (X2) at 10(-8) M; LTB4 was active only at 10(-6) M (X1.9). These different curves suggest a specific effect on the release of LH-RH. Moreover, these effects were selective since no alteration of SRIF and GRF secretions was observed. No additive effect on LH-RH release was observed when LTC4 and LTD4 were added simultaneously at 10(-8) M. FPL-55712, a drug supposed to be an antagonist of LTC4, showed an unexpected stimulatory effect (X4.2 and 1.7-fold) on LH-RH release at 3.10(-5) and 10(-6) M, respectively. However, FPL-55712 did not alter the release of LH-RH induced with 10(-8) or 10(-16) M LTC4. These results extend our previous observations on the stimulatory action of LTC4 and are the first evidence of the stimulatory effect of LTD4 and LTB4 on the LH-RH release.