Effect of Captopril, an Inhibitor of the Converting Enzyme on Naloxone Induced Secretion of ACTH and LH in Man

Abstract

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 captopril 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.

Effects of Antihypertensive Drugs on Angiotensinase Activities in the Testis of Spontaneously Hypertensive Rats

“…In addition to the local impact of antihypertensive drugs, these eff ects may also be the consequence of systemic mechanisms involving the hypothalamic GnRH or/and pituitary gonadotrophins. In this regard, while it has been reported that captopril has no infl uence on LH release [ 28 ] , propranolol decreased plasma levels of LH in a dose-dependent manner in orchidectomized rats [ 29 ] . Components of the RAS have been reported to be located in testis such as angiotensinogen, renin, ACE, Ang II, AT 1 , and AT 2 receptors [ 4 , 5 ] .…”