Glutathione peroxidase activity in a healthy Canadian population. Effects of age, smoking and drinking habits, exercise and oral contraceptive use.

The activity of the enzyme glutathione peroxidase (SeGSHPx) has been suggested as an indicator of selenium status. The purpose of this study was to measure the activity of this enzyme in a large sample of healthy, free-living Canadians to determine normal distributions and the effects of age, smoking, and drinking habits, exercise, and the use of oral contraceptives (OCs) or estrogen replacement therapy. The population consisted of 386 self-selected subjects between the ages of 24 and 75. Erythrocyte SeGSHPx activity was 21.5 +or- 7 (Mean +or- SD) and 33.6 +or- 8U/g Hb and plasma activity was 226 +or- 31 and 214 +or- 38 U/L for males (n=239) and females (n=147), respectively. Erythrocyte activity was significantly higher in females and males (p0.01). The Se form of GSHPx accounted for 76% and 54% of total activity in plasma and erythrocytes, respectively. No differences due to age were seen in males, although plasma SeGSHPx, non-SeGSHPx, and total GSHPx activities were elevated in females 65 years of age and older. Cigarette smoking significantly elevated erythrocyte SeGSHPx and total activity in male subjects. This elevation did not vary with the amount smoked and was not seen in ex-smokers. Drinking elevated erythrocyte non-SeGSHPx and total activity in male subjects with the highest activity seen in drinkers who also smoked. No significant differences were seen with level of exercise except for a slight elevation with vigorous exercise. Estrogen use significantly elevated erythrocyte SeGSHPx, non-SeGSHPx, and total activities in both pre- and postmenopausal women. These data suggest that some lifestyle factors can have small but significant effects of GSHPx activity and must be controlled for when population-based surveys are being conducted.