Isoproterenol-induced changes in glutathione metabolism in the rat parotid gland.
Rat parotid glands were removed at timed intervals after intraperitoneal injection of isoproterenol (IPR). Reduced/oxidized glutathione ratios, glutathione peroxidase, glutathione reductase and amylase activities were determined. Parotid gland amylase content fell to less than 5 per cent of control values within 1 h after IPR, then slowly returned to control levels by 24 h. The ratio of reduced/oxidized glutathione was decreased at 2 h after IPR injection, returned to near control values at 6 h, then increased above control levels at 9, 12 and 24 h. Glutathione peroxidase activity was increased only at 12 h after injection of IPR, whereas glutathione reductase activity initially decreased, then reached peak values at 12 h. These results indicate that alterations in metabolic activity during the secretory cycle are accompanied by changes in the reduced/oxidized glutathione ratio and the activity of glutathione-metabolizing enzymes. Cellular events contributing to these alterations in glutathione metabolism may include exocytosis, endocytosis and membrane recycling, increased amino-acid transport and resynthesis of secretory proteins.