Summary
It has been previously shown that endogenous opioid peptides suppress human ACTH and
gonadotropins secretion via hypothalamic mechanism. Since the angiotensin converting
enzyme can participate in the metabolism of opioid peptides, this study examined the
action of Captopril, an angiotensin converting enzyme inhibitor, on corticotropin
and gonadotropin (LH and FSH) release induced by the opiate antagonist naloxone in
man. Seven male hypertensive volunteers (aged 30-52) were treated with A) saline;
B) naloxone 8 mg iv as a bolus followed by an iv infusion of 4 mg/h; C) naloxone as
above after pretreatment with captopril 150 mg/day for 15 days; D) captopril alone.
Naloxone significantly stimulated ACTH and LH secretion when compared with the saline
infusion. This stimulating effect was taken as an indirect evidence for a tonic opioid
inhibition on pituitary hormones release. The pre-medication with captopril significantly
enhanced the ACTH and LH response to the opiate antagonist naloxone, but capropril
alone did not modify ACTH and LH values when compared to saline. The results would
suggest that captopril interferes with the opioid regulation of human ACTH and LH
secretion probably by blocking the proteolytic degradation of opioid peptides.
Key words
Opioid Peptides - Angiotensin Converting Enzyme - Corticotropin - Gonadotropins
