Effect of protein-free diet on activities and subunits of glutathione S-transferase in livers of young and aged female rats.
Female Fischer-344 rats of different ages (8 and 25 months old) were fed a protein-free diet (PFD) for 7 days and refed a normal diet (ND) (23% protein) thereafter. Rats were killed immediately after the PFD was stopped (day 0) and at different time intervals during refeeding of a ND. Four subunits (1,2,3 and 4) and activities of glutathione S-transferases (GSTs) toward five different substrates, [styrene oxide (STOX), 1,2-dichloro-4-nitrobenzene (DCNB), 1-chloro-2,4-dinitro benzene (CDNB), sulfobromophthalein (BSP) and benzalacetone (PBO)] were determined. There were no significant differences between young and old rats in the liver enzyme activities before the PFD. The PFD caused significant decreases in activities for three substrates (DCNB, BSP and STOX) in both age groups, with no significant differences between young and old rats a day 0. During recovery from the PFD, activities for the three substrates exceeded basal levels in young rats but at different time intervals (STOX, day 2; BSP, day 5; DCNB, day 9), while enzyme values in old rats tended to return slowly to basal values with no "overshoot." Concentrations of subunits 3 and 4 in young rat livers that were depressed by the PFD did not recover until day 9 of the ND, while subunits 2 and especially 1 increased during the ND refeeding, overshooting the basal levels. In contrast, in old rat livers the only change was a reduction of subunit 1 by the PFD and its gradual recovery during ND refeeding. These results demonstrate that our previous observation of overshooting of enzyme activities in mice is reproducible in rats but with certain substrate specificities. Furthermore, changes in subunit concentrations caused by aging and a PFD are more complex than what was predicted from changes in enzyme activities of GSTs.
Carrillo
M C
MC
First Laboratory of Clinical Physiology, Tokyo Metropolitan Institute of Gerontology, Japan.
Nokubo
M
M
Sato
Y
Y
Kanai
S
S
Ohta
M
M
Kitani
K
K
D000375:Aging / Q000378:metabolism*; D000818:Animals; D004044:Dietary Proteins / Q000008:administration & dosage; D005260:Female; D005982:Glutathione Transferase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D011487:Protein Conformation; D051381:Rats; D011916:Rats, Inbred F344; D013379:Substrate Specificity
D004044:Dietary Proteins; D005982:Glutathione Transferase