Poly(ADP-ribose) metabolism in proliferating versus quiescent cells and its relationship to their radiation responses.
In the murine tumour cell lines 66 and 67 growing in vitro, quiescent (Q; unfed plateau-phase) cells are more sensitive to X-ray-induced cell killing than are proliferating (P) cells, while St4 cells (Q cells that have been re-fed and returned to 37 degrees C for 4h) are similar to P cells in radiosensitivity. We have been investigating parameters of poly(ADP-ribose) metabolism in order to determine whether such factors contribute to the variations in radiosensitivity of these growth states. These parameters were cellular NAD content, the activity of poly(ADP-ribose) transferase (ADPRT) in permeabilized cells and the activity of poly(ADP-ribose)-degrading enzymes. The results suggest that in line 66, but not 67, a reduced ability to regenerate NAD following irradiation was associated with the reduced survival of Q cells. However, neither the baseline activity of ADPRT nor the degree of stimulation of ADPRT by X-rays was found to correlate with survival, or with the induction and repair of DNA strand breaks. Stimulation of ADPRT by X-rays was dependent on dose and was greatest for a 2-min incubation with 3H-NAD. For a 2-min incubation the stimulation of ADPRT following a dose of 50 Gy was 7- and 10-fold in 66 and 67 P cells, respectively, versus 3-4-fold in Q cells. Detectable stimulation was observed in 66 P and Q cells for doses as low as 5 Gy. P and Q cells did not differ in the rate of degradation of the poly(ADP-ribose) polymers.
Sweigert
S E
SE
Department of Radiology, University of Utah Health Sciences Center, Salt Lake City 84132.
Marston
J M
JM
Dethlefsen
L A
LA
D000818:Animals; D002453:Cell Cycle; D002455:Cell Division; D002470:Cell Survival / Q000528:radiation effects*; D066298:In Vitro Techniques; D007399:Interphase; D051379:Mice; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism*; D011064:Poly Adenosine Diphosphate Ribose / Q000378:metabolism*; D011836:Radiation Tolerance; D014407:Tumor Cells, Cultured / Q000166:cytology
D009702:Nucleoside Diphosphate Sugars; D011064:Poly Adenosine Diphosphate Ribose