Liver gamma-glutamyltranspeptidase activity and glutathione levels in lactating rats and pups: Effect of dietary protein quantity and feed intake

Abstract

Liver gamma-glutamyltranspeptidase (GGT-EC 2.3.2.2) activity and reduced glutathione (GSH) levels were measured on the delivery day (day 1) and in the middle of lactation (day 10) in rats. These rats were fed during gestation and up to the 10th day of lactation diets that varied in both protein quantity (25% versus 6% casein) and feeding level (ad libitum versus pair-fed 50% of ad libitum 25% casein intake). Just after birth (day 1 of lactation) there was a reduction ( P < 0.05) of GGT activity in dams, returning to the highest nonpregnant values at day 10 of lactation, independent of diet. In their pups, the enzyme activity was high at day 1 but decreased sharply at day 10. Not only the effect of protein restriction (6% casein) but also the energy intake restriction (50% of ad libitum 25% casein intake) were significant ( P < 0.01) at the delivery day, leading to an increase in the liver GGT activity in dams. A significant rise of the pups' GGT activity was promoted by the protein restriction at day 10. GSH was significantly reduced ( P < 0.01) by protein deprivation at day 10 in both lactating dams and pups. This decrease was associated with alterations in the enzyme activity only for the pups. Althogh no clear interrelationship could be established between the liver GGT activity and the GHS content, these results indicate a special influence of protein malnutrition on both parameters at lactation.