Fig. 6. Alterations in Rb phosphorylation in parental and clone-4 cells exposed to RA. (A) Total cell lysates from parental or clone-4 cells were immunoprecipitated with an anti-Rb antibody and western blotted with an anti-phospho-Rb monoclonal antibody. (B) Immunoprecipitate densitometric analysis of the proportion of PRb to total Rb from parental cells treated with RA and the NO donor DETA-NONOate (200 µM) or the cGMP analog 8Br-cGMP (250 µM), and from clone-4 cells treated with RA and L-NAME (5 mM). Bars are means±s.e.m. of four experiments. ^*, P<0.01 compared with control (Bonferroni's test after ANOVA).