Adrenergic Mechanism in Tetrahymena Iii Cyclic Adenosine 3', 5'-Monophosphate and Cell Proliferation

Abstract

Abstract-The presence of cyclic adenosine 3', 5'-monophosphate (cAMP) in the ciliated protozoan, <I>Tetrahymena pyrifurmis</I> W, was demonstrated by thin-layer chro matography (TLC). The content of cAMP in the cell increased abruptly in the early exponential phase, and then diminished with further culture. When cells in the ex ponential or stationary growth phase were cultured in a fresh medium, growth was inhibited by addition of dibutyryl cAMP (Bt<SUB>2</SUB>-cAMP) or methylxanthines.In syn chronized cultures of <I>Tetrahymena</I>, Bt<SUB>2</SUB>-cAMP inhibited protein and RNA syntheses in the G<SUB>1</SUB> phase and DNA synthesis in the S phase. These results indicate that cAMP regulates the growth of the protozoan in the G<SUB>1</SUB> phase.Earlier studies on the relationship between cAMP and cell growth showed that cAMP and its analog, Bt2-cAMP, inhibited growth of several types of tumor cells (1, 2). In the last few years much evidence has accumulated that cAMP participates in regulation of cell growth.On the other hand, it was found that Tetrahymena, a protozoan in which the meta bolic pathway of catecholamines is the same as in mammals (3, 4), has both cAMP phos phodiesterase (5) and adenyl cyclase (6) activities. Recently, Iwata et al. (7) obtained results suggesting that the adrenergic mechanism in Tetrahymena may be involved in control of growth in the late G, and G, phases. Therefore, we estimated the cAMP con tent in the protozoan and examined the effects on growth of several compounds affecting the cAMP system. MATERIALS AND METHODSThe method of culture and synchronization of Tetrahymena has been reported pre viously (8).cAMP in the protozoan was assayed as follows. Cells were harvested by centrifuga tion and after addition of 10 Vol. 6 % trichloroacetic acid, the sample was stored at 22'C, after which it was thawed and recentrifuged. The supernatant fraction was washed 3

Phylogeny and Ontogeny of Hormone Receptors: The Selection Theory of Receptor Formation and Hormonal Imprinting

“…of Tetrahymena, to some hormones of higher animals can nevertheless result in interaction, followed by a demonstrable response. This takes place when Tetrahymena is treated with epinephrine (Iwata & Kariya, 1973; Kariya, Saito & Iwata, 1974; Kassis & Kindler, 1975; Rosenzweig & Kindler 1972) or serotonin (Rosenzweig & Kindler, 1972), and also during the action of the juvenile hormone on Chritidia (Injeyan & Meerowitch, 1974).…”

Cyclic AMP metabolism in the cell cycle of tetrahymena pyriformis

“…These studies [4][5][6][7][8][9][10][11][12][13][14] have implicated cyclic AMP as a possible regulator of the cell cycle of Tetrahymena pyriformis. However, no direct measurement of cyclic AMP in the cell cycle of this organism has been made.…”