Insufficient activation of adrenocortical but not adrenomedullary hormones during stress in rats subjected to repeated immune challenge.

We have tested the hypothesis that chronic inflammatory stress results in changes in sympathoadrenal and renin-angiotensin-aldosterone responses to novel stressors. Repeated treatment of rats with increasing doses of lipopolysaccharide (LPS) resulted in a decrease of plasma adrenaline and aldosterone as well as in renin activity (angiotensin I) responses compared to those after acute administration. Repeated LPS administration was associated with decreased plasma aldosterone responses to a different stressor (immobilization) in spite of preserved or even elevated responses of plasma renin activity and catecholamines. These alterations may contribute to the development of cardiovascular complications during chronic inflammatory states.