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

ABSTRACT

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