Differential incorporation of 3H-thymidine into DNA in cultured skin fibroblasts derived from patients with cystic fibrosis and controls.

Tritiated thymidine (3H-TdR) incorporation into DNA of the fibroblasts derived from subjects 
with cystic fibrosis (CF) and their controls was studied with scintillation 
counting and autoradiography. 3H-TdR incorporation at 24 hours postseeding was significantly 
less (p < 0.005) in CF strains in comparison with cells 
from controls. The percentage of labeled fibroblasts was not significantly difference 
between the two strains (p > 0.1). The cell cycle time 
and the duration of each phase were studied by a mitotic 
selection and scintillation counting technique. There was no difference in cell 
cycle time between CF and control fibroblasts, however, the duration of 
the synthetic phase was significantly (p < 0.005) longer in CF 
subjects. 