Abstract
Stress is known to inhibit luteinizing hormone (LH) secretion, possibly via the actions of adrenocorticotrophin (ACTH) or corticotrophin releasing hormone (CRH). The aim of the present study was to investigate whether ACTH 1–39 or CRH could influence tonic and/or gonadotrophin releasing hormone (GnRH) induced LH secretion from the ovine pituitary in vitro. Perifused pituitaries ( n = 44 chambers) from mature ewes were given two GnRH challenges (5 × 10 −10 M): the first 45 min after sampling began and the second 2.5 h later. Some were perifused from 15 min prior to the first GnRH challenge with medium containing either 10 −7 M ( n = 8) or 3.75 × 10 −8 M ( n = 7) ACTH 1–39, or 2.5 × 10 −8 M ( n = 12) CRH. Results were expressed as a percentage of baseline values within a chamber. Neither of the two doses of ACTH 1–39 nor CRH had an effect on tonic LH secretion (control, 99.5 ± 5%; ACTH, 96 ± 8% and 97.5 ± 11%, respectively; CRH, 103 ± 11%) or the initial GnRH-induced LH secretion (control, 1049.1 ± 18.6%; ACTH, 1110.6 ± 352.2% and 1237.1 ± 610%, respectively; CRH, 1040.9 ± 240.7%). However, the LH response to the second GnRH challenge was significantly ( P < 0.001) inhibited (control, 1574.6 ± 224.9%; ACTH, 915.3 ± 426% and 1055.7 ± 326.4%, respectively; CRH, 857.1 ± 192%). Both doses of ACTH 1–39 significantly ( P < 0.001) inhibited the degree of GnRH self-priming, as did CRH (control, 152.4 ± 22.8%; ACTH, 79.3 ± 17.2% and 91.0 ± 18.5%; CRH, 82.8 ± 7.6%) when the second LH response was expressed as a percentage of the first LH response. In conclusion, both ACTH 1–39 and CRH had no effect on tonic LH secretion, but inhibited GnRH-induced LH secretion by preventing GnRH self-priming. The actions of CRH could be direct or be mediated by ACTH.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call