title: Stimulation of poly(ADP-ribosyl)ation during Ehrlich ascites tumor cell "starvation" and suppression of concomitant DNA fragmentation by benzamide.
abstract: Incubation of Ehrlich ascites tumor cells in their own ascites fluid induced a reversible metabolic adaptation to these "starvation" conditions which was associated with a fragmentation of DNA. Endogenous poly(ADP-ribose) residues also increased, reaching within 1-3 h values 6-10 times higher than in cells taken directly from the mouse peritoneum. The NAD content changed only slightly while dimethyl sulfate-induced accumulation of poly(ADP-ribose) (10-fold within 30 min) was associated with a rapid depletion of NAD (85% lost at 30 min). Nevertheless, turnover of poly(ADP-ribose) as measured by the decay rate of the polymer upon addition of benzamide was dramatically stimulated in both situations, reaching apparently identical half-lives (t 1/2 approximately equal to 1 min) in "starved" and in alkylated cells. However, since penetration of benzamide into the nucleus may be the rate-limiting factor in these studies, turnover of poly(ADP-ribose) in dimethyl sulfate-treated cells may still be much higher than that in "starved" cells. In cells treated with dimethyl sulfate, suppression of poly(ADP-ribose) synthesis by benzamide did not interfere with DNA fragmentation or with DNA resealing as determined by the nucleoid procedure. By contrast, starvation induced a type of DNA incision that was prevented by benzamide. It is proposed that starvation-induced scission of DNA occurs at specific ("regulatory?") sites requiring poly(ADP-ribose) formation to take place, while fragmentation of DNA at random as seen with alkylating agents is associated with, but not dependent on, increased poly(ADP-ribosyl)ation.
mesh_terms: D000818:Animals; D001549:Benzamides / Q000494:pharmacology*; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D004273:DNA, Neoplasm / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D009243:NAD / Q000378:metabolism; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism*; D011064:Poly Adenosine Diphosphate Ribose / Q000378:metabolism*
chemical_list: D001549:Benzamides; D004273:DNA, Neoplasm; D009702:Nucleoside Diphosphate Sugars; D009243:NAD; D011064:Poly Adenosine Diphosphate Ribose; C037689:benzamide