[The kinetic characteristics of the erythrocyte glutathione S-transferase system as a function of sex and the tobacco habit].
BACKGROUND
Erythrocytic glutathion S-transferase (GST) plays an important role as a protective mechanism against oxidative stress. The present study was conducted to evaluate the influence of both smoking habit and sex upon the kinetic characteristics of the enzyme.


METHODS
176 healthy subjects (100 men and 76 women), smokers and nonsmokers, were included. Enzyme parameters were calculated in erythrocytic haemolysates using 1-chloro-2,4-dinitrobenzene (CDNB) and glutathion (GSH) as substrates. Haemoglobin (Hb) was removed by affinity chromatography. In samples coming from 51 men and 42 women the native haemolysate was subjected to thermal shock (52 degrees C) and the enzyme parameters were compared with those obtained in the non-denatured samples.


RESULTS
In non-denatured samples, Km (mM) and Vmax (mumol/min/g Hb) values for CDNB were significantly higher (p < 0.001) in smokers than in non smokers, especially in women. Thus, respectively for Km and Vmax (mean +/- standard deviation): for men non smokers, 1.43 +/- 0.54, 1.63 +/- 0.42 and smokers, 1.74 +/- 0.5, 1.8 +/- 0.69; for women, non smokers 1.42 +/- 0.56, 1.57 +/- 0.46 and smokers, 2.05 +/- 0.59, 2.51 +/- 0.6. Thermal denaturation diminished the enzyme activity in all cases and modified the Km values, these results were opposite to those obtained in the non-denatured samples. Thus, for Km and Vmax respectively: for men, smokers, 1.6 +/- 0.71 and 0.9 +/- 0.32 and non smokers, 1.4 +/- 0.66 and 0.53 +/- 0.29; for women, non smokers, 2.00 +/- 0.58, 1.13 +/- 0.29 and smokers 1.22 +/- 0.77, 0.52 +/- 0.23. The GSt content was similar in the four groups studied (3.75 +/- 1.15 mumol SH/g Hb).


CONCLUSIONS
The greater thermolability of GST activity and the increase in the Km values observed in smokers, especially in women, should be considered as indicative of an increased risk for the erythrocytes against oxidative stress.
Ortín
F
F
Unidad de Farmacología, Facultad de Medicina, Universidad Rovira i Virgili, Reus, Tarragona.
Giralt
M
M
Cervelló
I
I
Nogués
M R
MR
Puerto
A M
AM
Argany
N
N
Mallol
J
J
D000328:Adult; D000704:Analysis of Variance; D004912:Erythrocytes / Q000201:enzymology*; D005260:Female; D005978:Glutathione / Q000097:blood; D005982:Glutathione Transferase / Q000097:blood*; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007700:Kinetics; D008297:Male; D012016:Reference Values; D012727:Sex Characteristics; D012907:Smoking / Q000097:blood*; D018709:Statistics, Nonparametric
D006454:Hemoglobins; D005982:Glutathione Transferase; D005978:Glutathione
Características cinéticas del sistema glutatión S-transferasa eritrocitario en función del sexo y del hábito tabáquico.