The effect of vitamin E, L-arginine, N-nitro L-arginine methyle ester and Forskolin on endocrine and metabolic changes of rats exposed to acute cold stress

OBJECTIVE: It is a well documented fact that under stress conditions the hypothalamic-pituitary-adrenal axis (HPA) and the sympathetic nervous system (SNS) are stimulated. This results in a series of neural and endocrine adaptations known as the stress response. The current study assessed the effects of acute cold stress on adrenomedullin (ADM) levels in plasma and peripheral tissues (kidneys and heart) of rats, as well as on blood glucose, cholesterol, triglycerides (TG), total proteins both before and after intraperitoneal administration of each of the following: vitamin-E, L-arginine, forskolin and L-NAME.

METHODS: The current study was conducted in the Department of Physiology, Faculty of Medicine, King Saud University, Saudi Arabia, between September 2003 and March 2004. We observed 6 groups of Wistar rats for their plasma ADM, tissue plasminogen activator (t-PA), total protein, glucose and cholesterol levels. Following exposure to cold stress (-10 degree celcius for 3 hours).

RESULTS: Acute cold stress produced a significant increase in ADM levels in plasma, heart and kidney tissues of rats. Furthermore, acute cold stress produced a reduction in cholesterol and plasma protein levels. On the other hand, acute cold stress caused an increase in TG, glucose plasma levels and tissue plasminogen activator (t-PA). We found hormonal and metabolic changes caused by cold exposure to be decreased or even prevented after vitamin E treatment or after changing nitric oxide (NO) level by L-arginine or L-NAME treatment.

CONCLUSION: The results suggest a regulatory or protective role for ADM in counteracting HPA activation following a variety of physiological and psychological stressors. Oxidative stress or changes in intracellular signals as NO, cyclic-AMP may play a role in explaining some of the metabolic and hormonal changes occurring during acute cold stress.