© 2001 National Science Council, ROC and S. The effect of endogenous adenosine on catecholamine secretion from the adrenal medulla is achieved partially through the inhibitory effect of adenosine on the renin-angiotensin system. These results demonstrate that under basal physiological conditions, endogenous adenosine tonically inhibits catecholamine secretion from the adrenal medulla, and this effect is augmented when the sympathetic system is stimulated. The effect of DPSPX on plasma catecholamine in rats pretreated with captopril (an angiotensin-converting enzyme inhibitor) was reduced. Finally, we tested whether endogenous adenosine restrains catecholamine secretion partially through inhibiting the renin-angiotensin system. The effect of DPSPX and insulin on epinephrine in adrenalectomized rats was significantly reduced compared with that of the controls.

Additional experiments were performed in adrenalectomized rats to investigate the contribution of the adrenal medulla to the effect of DPSPX on plasma catecholamine. The effect of DPSPX on plasma catecholamine was significantly greater in rats treated with insulin. DPSPX significantly increased plasma catecholamine in both control rats and rats treated with insulin. Plasma catecholamines were measured by HPLC with an electrochemical detector. The effects of an adenosine receptor antagonist, 1,3-dipropyl-8-( p-sulfophenyl) xanthine (DPSPX), on epinephrine and NE release induced by intravenous administration of insulin in conscious rats were examined. The purpose of this study was to examine whether endogenous adenosine restrains NE and epinephrine release from the adrenal medulla.

Adenosine was shown to inhibit norepinephrine (NE) release from sympathetic nerve endings.

Catecholamines adrenal medulla