NITRIC-OXIDE MEDIATES GONADOTROPIN-RELEASING-HORMONE EFFECTS ON FROG PITUITARY

Citation
A. Gobbetti et M. Zerani, NITRIC-OXIDE MEDIATES GONADOTROPIN-RELEASING-HORMONE EFFECTS ON FROG PITUITARY, Journal of neuroendocrinology, 10(6), 1998, pp. 407-416
Citations number
41
Categorie Soggetti
Neurosciences,"Endocrynology & Metabolism
ISSN journal
09538194
Volume
10
Issue
6
Year of publication
1998
Pages
407 - 416
Database
ISI
SICI code
0953-8194(1998)10:6<407:NMGEOF>2.0.ZU;2-4
Abstract
We studied the possible role of nitric oxide (NO) in GnRH-induced gona dotropin secretion in the female water frog, Rana esculenta. During pr e-reproduction, pre-ovulation, ovulation, post-ovulation, refractory, recovery and hibernation, pituitaries were incubated with medium-alone , GnRH, NO donor (NOd), NO synthase inhibitor (NOSI), cyclic GMP analo gue (cGMPa), soluble guanylate cyclase inhibitor (sGCi), GnRH plus NOS I, GnRH plus sGCi, and NOd plus sGCi. Because antisera raised against gonadotropins are not available for this species, we measured these ho rmones indirectly through their effects on ovarian progesterone secret ion. The ovaries were superfused with the pituitaries pre-incubated as reported above, In addition, NOS activity and cGMP levels were determ ined in the pre-incubated pituitaries. Those pre-incubated with medium -alone and with GnRH increased progesterone secretion during pre-repro duction, pre-ovulation, ovulation and recovery; the increase induced b y GnRH was higher than that induced by medium-alone during pre-reprodu ction, pre-ovulation and recovery. NOd and cGMPa increased progesteron e in all considered reproductive phases except ovulation; the increase induced by NOd and cGMP was higher than that induced by medium-alone during pre-reproduction, pre-ovulation and recovery, NOS activity was highest during ovulation and lowest during post-ovulation, refractory and hibernation, GnRH increased NOS activity during pre-reproduction, pre-ovulation and recovery. Cyclic GMP levels were highest during ovul ation and lowest during post-ovulation, refractory and hibernation. Gn RH increased cGMP levels during pre-reproduction, pre-ovulation and re covery, NOd during all considered reproductive phases. These results s uggest that NO mediates basal and GnRH-induced gonadotropin secretion in female Rana esculenta.