Objectives:This study has a twofold aim: 1) to investigate whether protein expression and enzyme activity of phosphodiesterase 4 (PDE5) can be detected in human myometrium and undergo changes in relation to the presence of pregnancy and/or labor; 2) to evaluate whether PDE 5 expression and activity in myometrial cells can be influenced by human chorionic gonadotropin (HCG).
Methods:Primary cultures of myometrial cells, obtained from non-pregnant women and from pregnant women at tem, either before or during labor, were carried out in the presence of HCG or dibutyryl-cyclic AMP (ad-cAMP), the non-hydrolizable analogue of cAMP. PDE5 expression in cultures of myometrial cells was detected by immunocytochemistry and western blot. PDE5 activity was detected in cell extracts by enzyme assay.
Results:PDE5 is expressed and is functionally active in smooth myscle cells. Treatment of cell cultures with HCG and db-cAMP results in a reduction of PDE5 expression and activity. The effects of HCG and db-cAMP are exerted irrespective of the functional status of the myometrium (n0n-pregnant, pregnant not in labor, pregnant in labor).
Conclusions:PDE5 protein is expressed in human non-pregnant and pregnant myometrium. HCG reduces PDE5 expression and enzyme activity in smooth muscle cells, possibly through a pathway involving cAMP
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