Leukotriene B4-induced human melanocyte pigmentation and leukotriene C4-induced human melanocyte growth are inhibited by different isoquinolinesulfonamides.

Leukotriene C4 (LTC4) is known to be a potent mitogen for cultured human neonatal melanocytes. We now demonstrate that leukotriene B4 (LTB4) can induce pigmentation in cultured human neonatal melanocytes in a dose-dependent fashion. The LTC4-induced mitogenesis is blocked by the cyclic nucleotide-dependent kinase inhibitor N-[2-(methyl-amino)ethyl]-5-isoquinolinesulfonamide dihydrochloride (H8). The LTB4-induced pigmentation is blocked by the protein kinase C inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H7). We propose that LTB4-induced pigmentation and LTC4-induced mitogenesis are important in vivo signals. Their different effects in our culture system are blocked by different protein kinase inhibitors.