Pharmacological manipulation of nitric oxide levels in mouse follicle cultures demonstrates key role of extrafollicular control of ovulation.
BACKGROUND
Nitric oxide (NO) is involved in ovulation, but it is uncertain whether the mechanisms responsible are systemic or local. In vivo and in perfused ovaries, inhibition of nitric oxide synthase (NOS) reduces ovulation. This study used a well-characterized system of isolated follicle culture to assess which isoforms of NOS might be involved at the follicular level.


METHODS
NOS inhibitors, stimulators and NO donors were used to manipulate the environment of mouse cultured follicles, selectively targeting different isoforms of NOS. Follicle survival and ovulation in vitro were monitored using established markers.


RESULTS
Inhibition of endothelial NOS did not affect survival or ovulation of cultured follicles. Inhibition of inducible nitric oxide synthase (iNOS) had mild effects in this system, generally inhibitory of ovulation. NO donors had variable inhibitory effects, including toxic effects. Stimulators of iNOS appeared to show mixed, mostly inhibitory, effects that possibly involved different mechanisms.


CONCLUSIONS
The results suggest that relatively minor effects on survival and ovulation in vitro are achieved by modulating the NO pathway, and the marked effects of NOS inhibitors in vivo do not occur in vitro. It is therefore probable that the effects of NOS inhibitors in vivo are mediated via effects outside the follicle.
Mitchell
Leila M
LM
Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK.
Kennedy
C Richard
CR
Hartshorne
Geraldine M
GM
D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007375:Interleukin-1 / Q000494:pharmacology; D007550:Isothiuronium / Q000031:analogs & derivatives* / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D008815:Mice, Inbred Strains; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D019335:Nitroarginine / Q000494:pharmacology; D009603:Nitroso Compounds / Q000494:pharmacology; D009924:Organ Culture Techniques; D006080:Ovarian Follicle / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D010060:Ovulation / Q000187:drug effects* / Q000502:physiology*; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D019323:omega-N-Methylarginine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D007375:Interleukin-1; D008070:Lipopolysaccharides; C093285:NOC 18; D020030:Nitric Oxide Donors; D009603:Nitroso Compounds; D019335:Nitroarginine; D007550:Isothiuronium; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496317:Nos2 protein, mouse; C496315:Nos3 protein, mouse; C027744:S-methylisothiopseudouronium; D019331:NG-Nitroarginine Methyl Ester