Abstract
Growth of Tetrahymena in the exponential phase was slightly accelerated by transfer of cells to a medium containing 10-3-10-5 M adrenaline or noradrenaline, while that of stationary phase cells was inhibited by 10-3-10-7 M catecholamine. In synchronized cultures of Tetrahymena, adrenaline inhibited RNA and protein syntheses in both the late G1 and the G2 phases. These inhibitory effects in the late G1 and G2 phases result in an inhibition of the introduction of the S phase and of cytokinesis, respectively. These results indicate that an adrenergic mechanism in Tetrahymena plays a role in regulating the cell cycle.
