Transient nature of histamine receptor induction in human blood monocytes. Blood was taken from one volunteer (E in Table 1) and monocytes were isolated. The following day, the cells were either left unstimulated (open circles) or stimulated with LTE4 (100 ng/ml) for 5 min (A), 15 min (B) or 30 min (C) (filled circles). (D) Amount of histamine H1 receptors at the indicated time intervals. Scatchard analysis was performed to determine number of receptors per cell as described in Materials and Methods.