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Abstract |
The Nitric Oxide/Cyclic Guanosine Monophosphate System in Human Myometrium at Term |
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We investigated the role of cyclic guanosine monophosphate (cGMP) in response to endogenous and exogenous nitric oxide (NO) in human labor at term. Therefore we developed a reliable procedure for preparation of human myometrium and determination of its cGMP content. NO-synthase activity and the influence of various substances on cGMP production was measured in myometrial tissue samples of women at term undergoing caesarean section before or after the onset of labor. Storage conditions and homogenization techniques signifrcantly influenced the extraction of cGMP. Neither myometrial NO-synthase activity nor cGMP production (with and without 3-isobutyl-1-methylxanthine, an inhibitor of cGMP hydrolysis by phosphodiesterase) differed between laboring and non-laboring women. Moreover, exogenous application of NO (via the NO-donor 3-morpholinosydnonimine) increased cGMP production similarly in tissue from women with and without labor pains. Applying the described procedure for tissue preparation we provide the first evidence that basal and NO-induced cGMP production is not different in myometrium obtained from women at term with and without labor pains. Our results argue against an important role of the NO/cGMP system in human labor at term. |
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