Decrease in Urinary Excretion of Ascorbic Acid and Histamine in Rats after Repeated Immobilization Stress

Abstract

Feeding rats an ascorbic acid-free diet led to a gradual decrease in urinary excretion of ascorbic acid, which reached an equilibrium of approximately 350 µg/day/100 g of body weight after 18 days. The urinary level of histamine also decreased steadily on this diet. Consecutive 4-hour daily immobilization stress resulted in a marked reduction in the urinary output of ascorbic acid in rats fed this diet: from 357 ± 6 µg/day per 100 g of body weight (mean ± SEM, n = 6) to 224 ± 13 (-37%, P < 0.01) after 6 days. The amount of ascorbic acid in the serum, liver and adrenal glands fell significantly. There was a marked reduction in urinary excretion of histamine under immobilization stress. Both urinary ascorbic acid and histamine tended to return toward their original values after cessation of the stress regimen. The implications of these observations are discussed in relation to a possible natural defense mechanism of animals against stressful stimuli.