Fig. 1.

Aging-associated changes in GSH/GSSG levels, nSMase activity, and ceramide species in liver. Young (5 months) and aged (23 months) C57Bl6 mice were randomly placed on either a Std chow or a SAA def. diet for 4 weeks. Twenty percent homogenates from livers were prepared and used for analyses. Hepatic GSH and GSSG (A, B, D, E) were measured in individual animals (n = 3) using a Bioxytech® GSH/GSSG-412™ assay kit as outlined in the Materials and Methods. nSMase activity (C, F) was measured in whole liver homogenates (40 μg of protein/assay) using a fluorescently labeled analog NBD-SM as a substrate. The mean values for each individual mouse are shown. Quantification of the different ceramide species in the liver of young and aged animals was done by HPLC-ESI/tandem mass spectrometry (G). Mean values ± SD are shown (n = 3), *P < 0.05, **P < 0.01 according to Student’s t-test.