Poly ADP-ribosylation of two mouse
lymphoma cell lines, L5178Y (LS) and the radiation and
alkylating agent resistant derivative AII, was investigated by uptake of [3H]
NAD by permeabilised cells into
acid-precipitable material that was sensitive to
phosphodiesterase but insensitive to
DNase and
RNase. Basal activities in both
lymphoma lines were 3-4-fold greater than in mouse L1210 leukaemia cells. However, total endogenous poly (
ADP-R) polymerase activity in both L5178Y cell lines, stimulated by a large excess of
DNase in the presence of
Triton X-100, was less than half the activity in L1210 cells. Doses of
N-methyl-N-nitrosourea (MNU) that produced 20-50% survival of colony-forming units increased poly (
ADP-R) in both
lymphoma lines by only 25% compared with 377% in L1210 cells when synthesis was measured immediately after a 30-min exposure of MNU. During the first 24 h after MNU AII cells produced a peak of activity that was not seen with LS cells. A second peak was seen in both cell lines between 24 and 48 h following MNU. Concentrations of
3-aminobenzamide (3AB) above 2.5 mM inhibited colony-forming ability of
lymphoma cells and equally inhibited uptake of [14C]
formate into
protein,
RNA and
DNA indicating that 3AB behaves as a general metabolic
poison. Concentrations of 3AB in the toxic range of 3-10 mM inhibited poly (
ADP-R) synthesis but no degradation of the
polymer was observed. Non-toxic concentrations of 3AB potentiated cell killing by MNU to a similar degree in both
lymphoma cell lines. In conclusion, we have found little evidence to support the hypothesis that the differential sensitivity of LS and AII is related to poly ADP-ribosylation. Compared with other mouse cells, L5178Y cells appear deficient in poly (
ADP-R) polymerase and poly (
ADP-R)
glycohydrolase activities.