Effect of oxytocin on nitric oxide activity controlling gonadotropin secretion in humans.
BACKGROUND
Previously described inhibitory effects of the nitric oxide synthase (NOS) inhibitor L-NAME on luteinizing hormone-releasing hormone (LH-RH)-induced LH and follicle stimulating hormone (FSH) secretion in humans suggested modulation by nitric oxide (NO) of the gonadotropin-releasing action of LH-RH.


METHODS
In order to establish whether oxytocin (OT) participates in this regulatory mechanism, 10 normal men were treated with LH-RH (100 micro g as an i.v. bolus) given alone or in the presence of L-NAME (40 micro g kg-1 injected plus 50 micro g kg-1 infused i.v. for 60 min), OT (2 IU injected plus 4 IU infused i.v. for 60 min) or a combination of both drugs.


RESULTS
The administration of OT was unable to change the gonadotropin responses to LH-RH. In contrast, L-NAME significantly reduced both FSH and LH increments induced by LH-RH. When L-NAME was given in the presence of OT, the LH and FSH responses to LH-RH were similar to those observed after the administration of LH-RH alone.


CONCLUSIONS
These data suggest antagonistic actions of OT and L-NAME in the control of NOS activity in regulation of gonadotropin secretion induced by LH-RH.
Chiodera
P
P
University of Parma, Parma, Italy.
Volpi
R
R
Manfredi
G
G
Bortesi
M L
ML
Capretti
L
L
Magotti
M G
MG
Saccanijotti
G
G
Coiro
V
V
D000328:Adult; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D010121:Oxytocin / Q000008:administration & dosage / Q000494:pharmacology*
D009569:Nitric Oxide; D007987:Gonadotropin-Releasing Hormone; D010121:Oxytocin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone