As part of an investigation into the role of leukotrienes in steroidogenesis, the formation of leukotriene B4 was investigated in purified Leydig cells from rat testes and from a tumour by using a sensitive radioimmunoassay. Detectable levels were found in both Leydig cell types (70 pg/10(6) cells) and these remain unchanged during incubation for 60 min at 32 degrees C. Addition of the Ca2+ ionophore A23187 increased LTB4 production more than 6-fold within 10 min whereas steroidogenesis was not increased until after 20 min. In the presence of luteinizing hormone or luteinizing hormone releasing hormone agonist no increase in LTB4 was detected in the testis Leydig cells whereas luteinizing hormone stimulated testosterone production from 3.2 +/- 0.1 to 148.9 +/- 7.5 ng/10(6) cells during the same time period. Similar results were obtained with the tumour Leydig cells. The LTB4 was found to be rapidly secreted by the cells in all experiments. The basal and A23187-stimulated levels were inhibited by nordihydroguaiaretic acid, a lipoxygenase inhibitor. It is concluded that LTB4 is produced in Leydig cells and can be stimulated by high calcium levels, but that it is probably not required for the control of steroidogenesis.

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