Increase in intracellular calcium induced by stimulating histamine H1 receptors in macrophage-like P388D1 cells

The addition of histamine to macrophage-like P388D1 cells resulted in a dose-dependent increase in intracellular calcium [Ca 2+] i measured by fura-2 in single cells. The maximum level of [Ca 2+] i was obtained by addition of 1×10 −4M histamine. The increase was primarily due to release from the intracellular store. The addition of an H1 specific antagonist pyrilamine before histamine treatment inhibited the increase reversibly, while an H2 specific antagonist cimetidine had no inhibitory effect. Histamine also resulted in a dose-dependent increase in cGMP but not in cAMP. These data suggest the existence of histamine H1 receptors in these cells and histamine may have some biological effect on the function of macrophages via [Ca 2+] i and cGMP as the second messengers.