Effect of pineal indoles on activities of the antioxidant defense enzymes superoxide dismutase, catalase, and glutathione reductase, and levels of reduced and oxidized glutathione in rat tissues.

Male Sprague-Dawley rats were randomly divided into four groups. Two of the groups received a single intraperitoneal injection of melatonin and 5-methoxytryptamine (5 mg/kg body weight), respectively, at 9 PM. One group received an intraperitoneal injection of 5-methoxytryptophol (5 mg/kg body weight) at 9 AM. The remaining group received alcoholic saline (vehicle) and served as the control. All rats were sacrificed 90 min after injection and the livers, kidneys, and brains were dissected. The activities of superoxide dismutase, catalase, and glutathione reductase in the organs were measured. It was found that both melatonin and 5-methoxytryptamine were approximately equipotent in enhancing the activities of superoxide dismutase and glutathione reductase in the kidney and liver, while 5-methoxytryptophol displayed a weaker effect. Both melatonin and 5-methoxytryptamine augmented the level of reduced glutathione in the kidney and liver, while 5-methoxytryptophol did so only in the kidney. All three pineal indoles increased the activity of superoxide dismutase and lowered the ratio of oxidized to reduced glutathione in the brain.