Inhibition of murine transformed Leydig cell proliferation by leukotrienes in serum-free culture.
We have previously shown that estrogen-dependent growth enhancement of murine transformed Leydig cells (B-1 F) is mediated through inhibition of arachidonic acid metabolite formation. In the present study, the growth-inhibitory ability of leukotrienes (LTs) on B-1 F cells in serum-free culture was directly addressed. All peptidyl LTs (LTC4, LTD4, and LTE4) inhibited B-1 F cell growth in a dose-dependent manner and exhibited maximum inhibition of DNA synthesis (60-80%) compared with that of untreated cells in a range of 10(-9) to 10(-8) M. To examine the mechanism of this LT-dependent inhibition, binding studies of LTD4 toward plasma membrane were conducted. Specific binding sites for LTD4 were identified. Scatchard analyses indicated the presence of a single class of high-affinity sites (Kd = 0.9 +/- 0.2 nM; maximum binding sites, 61 +/- 18 fmol/mg protein). This binding of LTD4 to the high-affinity site was markedly inhibited by ICI 198615, a specific inhibitor for LTD4. These results would suggest that inhibitory effects of LTs, at least LTD4, are elicited as a receptor-mediated event. In addition, this LT-dependent growth inhibition could not be blocked by simultaneous exposure of cells to estrogen, whereas estrogen partially protected arachidonic acid-dependent growth inhibition. Furthermore, treatment of cells with estrogen resulted in marked suppression of 5-lipoxygenase activity. Collectively, the present data clearly show that LTs play an important role as intermediates in an autocrine loop for B-1 F cells to exhibit estrogen-dependent growth.
Nishii
K
K
Third Department of Internal Medicine, Osaka University Hospital, Japan.
Nishizawa
Y
Y
Nishizawa
Y
Y
Matsumoto
K
K
Sato
B
B
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002461:Cell Line, Transformed; D016895:Culture Media, Serum-Free; D004247:DNA / Q000096:biosynthesis*; D004958:Estradiol / Q000494:pharmacology; D015289:Leukotrienes / Q000378:metabolism / Q000494:pharmacology*; D007985:Leydig Cells / Q000166:cytology* / Q000378:metabolism; D008297:Male; D010741:Phospholipases A / Q000378:metabolism; D011971:Receptors, Immunologic / Q000378:metabolism; D018077:Receptors, Leukotriene; D013189:SRS-A / Q000378:metabolism / Q000494:pharmacology
D016895:Culture Media, Serum-Free; D015289:Leukotrienes; D011971:Receptors, Immunologic; D018077:Receptors, Leukotriene; D013189:SRS-A; D016718:Arachidonic Acid; D004958:Estradiol; D004247:DNA; D010741:Phospholipases A