Opioid modulation of normal and pathological human chromaffin tissue.
To evaluate whether opioid receptor blockade might modulate sympathetic-adrenal activity, we studied the effects of placebo or naloxone administration on plasma catecholamine (CA) levels in a group of 13 normal subjects and 15 hypertensive patients suspected to have a pheochromocytoma. Diagnostic evaluation confirmed the presence of pheochromocytoma in 9 patients. Among these, 4 had a unilateral epinephrine (E)-secreting tumor, 3 had bilateral E-secreting tumors due to multiple endocrine adenomatosis type IIa, and 2 had a unilateral norepinephrine (NE)-secreting tumor. In each subject studied, CA secretion was evaluated by calculating the area (0-30 min) under the plasma hormone curves after placebo or naloxone administration. In normal subjects naloxone caused a significant increase (P less than 0.005) of E secretion, whereas NE did not change. Similarly, in the group of hypertensive patients, E secretion increased after naloxone (P less than 0.01). In pheochromocytoma patients naloxone caused a significant increase in E (P less than 0.05) and NE (P less than 0.01) secretion from E-producing tumors but no increase in the patients with NE-secreting pheochromocytomas. The study suggests that CA secretion from normal and pathological chromaffin tissue is modulated by endogenous opioids; this modulation seems particularly evident in patients with E-secreting pheochromocytoma.
D000293:Adolescent; D000310:Adrenal Gland Neoplasms / Q000097:blood; D000328:Adult; D000368:Aged; D002395:Catecholamines / Q000097:blood*; D002838:Chromaffin System / Q000378:metabolism*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000097:blood; D008297:Male; D008875:Middle Aged; D009270:Naloxone / Q000494:pharmacology; D010673:Pheochromocytoma / Q000097:blood; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*
D002395:Catecholamines; D011957:Receptors, Opioid; D009270:Naloxone