Effects of gamma-hexachlorocyclohexane and L-3,3',5-triiodothyronine on rat liver cytochrome P4502E1-dependent activity and content in relation to microsomal superoxide radical generation.
Liver microsomal cytochrome P4502E1-dependent p-nitrophenol (PNP) hydroxylation and expression of cytochrome P4502E1 were studied in rats subjected to gamma-hexachlorocyclohexane (HCCH) or L-3,3,5-triiodothyronine (T3) administration as a possible mechanism contributing to superoxide radical (O2.-) generation. HCCH treatment (a single dose of 40 mg/kg body wt) produced a 43% increase in the content of total cytochrome P450, whereas T3 (daily doses of 0.1 mg/kg body wt for two consecutive days) led to a 37% decrease. NADPH-dependent O2.- generation was elevated by HCCH and T3, expressed as either per mg of protein or per nmol of cytochrome P450, with a 135% enhancement in the O2.- production/superoxide dismutase (SOD) activity ratios being observed in both conditions. This was partly due to depression of SOD activity. Concomitantly, the molecular activity of NADPH-cytochrome p450 reductase was enhanced by 90 and 69% by HCCH and T3, respectively. In these conditions, microsomal PNP hydroxylation showed increases of 58 and 45% in HCCH- and T3-treated rats over control values, respectively, with a parallel 31% (HCCH) and 41% (T3) enhancement in the content of cytochrome P4502E1 assessed by western immunoblotting. We conclude that HCCH and T3 enhance the expression and activity of cytochrome P4502E1 and that of NADPH-cytochrome P450 reductase in rat liver, regardless of the changes in total cytochrome P450 content, representing major contributory mechanisms to microsomal NADPH-dependent O2.- generation.
Fernández
Virginia
V
Programa de Farmacología Molecular y Clínica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Casilla 70000, Santiago-7, Chile. vfernand@machi.med.uchile.cl
Massa
Laura
L
Quiñones
Luis
L
Simon-Giavarotti
Karin A
KA
Giavarotti
Leandro
L
D'Almeida
Vânia
V
Azzalis
Ligia A
LA
Junqueira
Virginia B
VB
Videla
Luis A
LA
D000818:Animals; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism*; D001556:Hexachlorocyclohexane / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology*; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species; D014284:Triiodothyronine / Q000494:pharmacology*
D017382:Reactive Oxygen Species; D014284:Triiodothyronine; D001556:Hexachlorocyclohexane; D019392:Cytochrome P-450 CYP2E1