In Vitro Analysis of the Participation of Oxytocin and Vasopressin in the Gonadotropin Releasing Hormone-Induced Release of LH 1 2

Summary

The pituitary perfusion technique was used to investigate the possible interaction between the neurohypophyseal hormones and gonadotropin releasing hormone (GnRH). The perifusion of rat anterior pituitaries with 0.2 mU/ml arginine vasopressin (AVP) resulted in a significant (P < 0.05) increase in LH release over baseline, while higher doses had no effect. When combined with GnRH, this and higher concentrations of AVP did not alter the GnRH-induced release of LH. Three concentrations of oxytocin (OT): 0.02, 0.2 and 20 mU/ml, increased baseline secretion of LH (P < 0.05) while 2 mU/ml OT did not. When added to GnRH-containing perifusion media, 0.02 mU/ml OT caused significant (P < 0.05) enhancement and prolongation of the LH response to GnRH. All higher concentrations of OT and one concentration that was tenfold lower, did not exhibit potentiating effects. When the pituitary tissue was pretreated with AVP or OT prior to stimulation with GnRH, only the same concentration of OT (0.02 mU/ml) was effective (P < 0.01) while two concentrations of AVP (2 and 20 mU/ml) which had been ineffective previously, then enhanced the LH release due to GnRH (P < 0.05 and P < 0.01, respectively). It is proposed that the data from these experiments support the hypothesis that AVP and OT may have a role in reproduction via an interaction with GnRH at the level of the anterior pituitary.