COOPERATIVITY OF HORMONES AND HORMONE-LIKE MATERIALS IN TETRAHYMENA

Triiodothyronine [T3], serotonin and gramine equally enhanced the growth of Tetrahymena at 10-9 M concentration, but equally depressed it at 10-5 M. Paired combinations of the hormones showed either positive or negative cooperation, as assessed from the influence on Tetrahymena growth. The chemically different T3 and gramine enhanced the effect of one another, while chemically related serotonin and gramine mutually depressed it. The cooperative interaction of serotonin and T3 also was negative.