Acute stressor-selective effect on total plasma homocysteine concentration in rats.

Stress produces several physiological and behavioral alterations that increase cardiovascular morbidity and mortality. Nonetheless, there is a dearth of studies that have evaluated the effects of stress on total plasma homocysteine, an important amino acid associated with cardiovascular disease. We used four distinct acute stressors in rats, i.e., swimming, restrain, novelty and cold exposure, in order to examine whether any acute effect on total plasma homocysteine concentrations would occur. Plasma corticosterone and adrenocorticotropic hormone concentrations were also measured to demonstrate the ability of the chosen manipulations to activate the hypothalamic-pituitary-adrenal (HPA) axis. Three of the four stressors activated the HPA axis and only restrain affected total plasma homocysteine concentrations (+37%, P=.006) compared with the control group. The complexity of the physiological responses to stress, the peculiarities of stress responses and the intricate regulatory systems involved in homocysteine metabolism must be taken into account in order to clarify the increasing effect of restrain (mainly a psychological stressor) on total plasma homocysteine concentrations in rats and to evaluate its meaning in human pathology.