Inhibition of adenylyl cyclases by 12(S)-hydroxyeicosatetraenoic acid

The inhibition of adenylyl cyclase (AC) by a 12-lipoxygenase metabolite of arachidonic acid, 12(S)-hydroxy-5Z,8Z,10E,14Z-eicosatetraenoic acid (12-HETE), was investigated using three different kinds of cells: NRK-49F (normal rat kidney fibroblasts), AtT-20 (mouse pituitary tumor cell line) and HL-60 (human leukemia cells) cells. The inhibition was very obvious in NRK-49F and AtT-20 cells, but it was almost negligible in HL-60 cells. There was no difference in terms of the binding of 12-HETE to NRK-49F and HL-60 cells. Pretreatment of NRK-49F cells with pertussis toxin almost completely ADP-ribosylated Gi proteins, but it did not affect the inhibition of 12-HETE on AC in this cell. This result excludes the involvement of Gi proteins in 12-HETE-mediated inhibition of AC. It was revealed that the characteristics of ACs in these cells were quite different in response to agonists and forskolin, suggesting that these cells do have different isoform of AC. We conclude that 12-HETE inhibits the activity of AC depending upon the isoform.