Antioxidant supplementation normalizes elevated protein kinase C activity in the proximal tubules of old rats.
Aging is associated with increase in oxidative stress. Earlier, we have shown that higher basal protein kinase C (PKC) activity in the proximal tubules (PTs) of old rats contributes to the hyperphosphorylation of Na,K-ATPase and subsequent decrease in basal Na,K-ATPase activity, resulting in diminished natriuretic response to dopamine in these animals. We hypothesized that the increase in PKC activity in PTs of old rats is caused by increased oxidative stress and that antioxidants administration should reduce/normalize the elevated PKC activity in the renal PTs of old rats. We studied the effect of two antioxidants, namely, alpha-lipoic acid (LA) and tempol, on oxidants level and PKC activity in the PTs of adult (6-month) and old (24-month) Fischer 344 rats. We found that the accumulation of fluorescent dichlorofluorescein (DCF), an indicator of oxidant production, was higher in the PTs of old compared to adult rats. Dietary supplementation with LA for 2 weeks normalized the increased DCF level in old rats. Carboxymethylysine and malondialdehyde, markers of oxidative damage, were elevated in the PTs of old rats, which were normalized to the level of adult rats when tempol was provided in drinking water for 3 weeks. Both LA and tempol treatment also normalized the higher basal PKC activity in the PTs of old rats to the level seen in adult rats. These results suggest that increase in oxidative stress causes an increase in PKC activity, and that antioxidants, while reducing oxidative stress, also normalize PKC activity in the PTs of old rats.
Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, Texas 77204, USA.
Mohammad
M
Asghar
Mustafa F
MF
Lokhandwala
D000375:Aging / Q000187:drug effects*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D003497:Cyclic N-Oxides / Q000494:pharmacology*; D019587:Dietary Supplements; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D011493:Protein Kinase C / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism; D013113:Spin Labels; D008063:Thioctic Acid / Q000494:pharmacology*
D000975:Antioxidants; D003497:Cyclic N-Oxides; D013113:Spin Labels; D008315:Malondialdehyde; D008063:Thioctic Acid; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase; C001803:tempol