AGE-DEPENDENT MODIFICATIONS OF MITOCHONDRIAL TRANS-MEMBRANE POTENTIALAND MASS IN RAT SPLENIC LYMPHOCYTES DURING PROLIFERATION

The specific fluorescent probes, Rhodamine 123 (Rh-123) and Nonyl-Acri dine Orange (NAO) were, respectively, used to monitor the changes in m embrane potential and mass of lymphocyte mitochondria during aging and proliferation. An age-dependent increase of the uptake of both fluoro chromes was observed in resting cells; however, NAO fluorescence incre ased to a greater extent when compared with the Rh- 123 probe. This re sulted in a lower respiratory activity per unit of mitochondrial mass in old cells than in the young ones. Following mitogenic stimulation, most of the lymphocytes from young rats showed an increase in their me mbrane potential and mass. On the contrary about 50% of cells from old rats had depolarized mitochondria after 72 h from the stimulation. Pr esent data support that mitochondria of lymphocytes from old rats are extremely sensitive to the stressing conditions resulting from mitogen ic stimulation.