Effects of hormones on the multiplication of the heterotrichous protozoon Blepharisma undulans stein.

The division rate of Blepharisma undulans is reduced by insulin treatment and increased by diiodotyrosine, diiodothyronin, histamine, serotonin or prednisolone treatment. In a later phase, the protozoa treated with histamine or prednisolone died. After insulin was deprived, the division rate strikingly increased as compared to the control cells, whereas the enhanced growth of the cells pretreated with any of the other hormones, except serotonin, continues in the absence of the hormone until the end of the observation period. The division rate of cells pretreated with serotonin decreased in the absence of the hormone. The cells of enhanced division rate hardly influenced by a second encounter with the same hormone, even insulin did not exert its characteristic negative effect. The fact that serotonin and insulin act in another way than do the other hormones suggests that the cell response is hormone-specific.