Histamine stimulates [Ca2+](i) oscillations in human aortic endothelial cells (HAEC), the frequency of which regulates the activity of nuclear factor-kappaB (NF-kappaB). This study was performed to determine whether phospholipase D (PLD) is involved in this signaling pathway. At a concentration of 1 muM, which stimulates [Ca2+](i) oscillations in this cell type, histamine initiated a twofold increase in [P-32]phosphatidybutanol (PBt), an index of PLD activity as early as 5 min after stimulation. During established [Ca2+](i) oscillations induced by 1 muM histamine, 0.3% n-butanol, which "functionally" redirects phosphatidic acid formed by PLD to PBt, decreased [Ca2+](i) oscillation frequency by similar to50% and produced a similar reduction in NF-kappaB activity. In the presence of the inositol 1,4,5-trisphosphate receptor blocker xestospongin C, which itself decreases the frequency of histamine-stimulated [Ca2+](i) oscillations, n-butanol produced a further decrease in oscillation frequency that was not associated with an additional reduction in NF-kappaB activity. This study shows that activation of PLD by histamine regulates [Ca2+](i) oscillation frequency and NF-kappaB activity in HAEC. (C) 2002 Elsevier Science (USA).