Variation of Ap4A and other dinucleoside polyphosphates in stressed Drosophila cells.

The unusual bis(5'-nucleosidyl)oligophosphates: Ap4A, Ap4G, Ap3A, and Ap3G, have been measured in cultures of Drosophila cells. Exponentially growing cells contain concentrations of 0.25, 0.31, 0.87, and 2.25 microM, respectively. These nucleotides have been followed after stressing the cells either by CdCl2 addition or by heat-shock treatment. Their concentrations are not affected by exposure to 500 microM CdCl2 during 6 h. Beyond this threshold of cadmium concentration, the nucleotides increase. With 5 mM CdCl2, an enhancement by 2 orders of magnitude of all the dinucleoside tri- and tetra-phosphates is observed. Upon heat-shock from 19 to 37 degrees C, Ap4A, Ap3A, and Ap3G increase up to 2.2, 3, and 3.3 times their initial levels, respectively. The increase is achieved within 1 h.