Changes of receptor cooperation in Tetrahymena by re-exposure to hormones

The hormone combination epinephrine + diiodotyrosine inhibited the growth of Tetrahymena cells on first exposure, but stimulated it markedly on re-exposure. It appears that amplification of the receptor by the hormone does take place at the first encounter, regardless of whether the response of the cells was positive or negative. The amplifying effect persists over several generations. The intensity of stimulation by the second exposure was directly related with the duration of the first one. Prolongation of the first exposure accounted for a switch-over from negative to positive influence.