| Abstract: | The intracellular content of cyclic 3 ,5-adenosine monophosphate (AMP) and activity of adenylate cyclase and cyclic AMP phosphodiesterase were determined in the lag period and the exponential and stationary phases of growth of mouse hepatoma 22a. In the stage of transition of the tumor cells from the lag period to the exponential phase of growth, the intracellular cyclic AMP concentration was found to be reduced by half as the result of sudden activation of phosphodiesterase. Later the cyclic AMP content fell more slowly until the cells entered the stationary phase of growth. Since adenylate cyclase activity remained unchanged during growth of the hepatoma 22a, this suggests that an increase in phosphodiesterase activity is the signal for escape of the tumor cells from the resting period and their entry into the mitotic cycle.Laboratory of Biochemical Pharmacology, Oncologic Scientific Center, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR L. M. Shabad.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny Vol. 84, No. 10, pp. 472–474, October, 1977. |
