Hormone receptor studies on frog macrophage cells by means of histamine, serotonin and indoleacetic acid.

The phagocytotic activity of frog macrophage cells could be increased by 50% with histamine and by 24% with serotonin. These hormones have a similar effect at the various stages of phylogenetic development, to judge from the respective responses of the unicellular Tetrahymena which showed roughly the same percentual increases of phagocytosis as frog macrophages at roughly the same hormone concentrations. It is concluded that cytoplasmic membrane receptor patterns for a given function do not change in the course of phylogenetic development and the receptors have a capacity for selection, preferring histamine to serotonin, and the latter to the chemically closely related plant hormone indoleacetic acid.