(a)
(b)
(c)
(d)
Figure 2: Cys and CySS concentrations in media conditioned by fibroblasts isolated from the lungs of young and old mice. (a) Cys and CySS concentrations in redox media at time 0 hours and (b) after 24 hours of incubation at 37°C in the absence of cells. (c) Cys and CySS concentrations in the conditioned media of fibroblasts from young and (d) old mice after 24 hours of incubation at 37°C.