Platelet-activating factor acetylhydrolase isoforms I and II in human uterus. Comparisons with pregnant uterus and myoma.
The concentrations of platelet-activating factor (PAF) that possesses the ability to stimulate myometrial contraction are partially regulated by intracellular type of platelet-activating factor acetylhydrolase (PAF-AH) in many tissues. Tissue cytosol contains at least two intracellular PAF-AH, isoforms I and II. To examine the relationship between the activity and isoforms of intracellular PAF-AH in human uterine myometrium and myoma, we assayed the PAF-AH activity and identified the PAF-AH isoforms I and II by Western blot analysis. The intense bands of the alpha2 and ss subunits of PAF-AH isoform I were detected in nonpregnant uterus; however, the specific bands of the alpha1 subunit of PAF-AH isoform I and the PAF-AH isoform II were extremely weak. The levels of the alpha2 and ss subunits and PAF-AH activity in pregnant uterus (37-39 wk gestation) were significantly lower than those in nonpregnant uterus. On the other hand, the level of ss subunit and the PAF-AH activity in myoma were significantly higher than those in nonpregnant uterus. No significant difference was found in the expression of the PAF-AH isoform II among three tissues. These results indicate that the change in the PAF-AH activity observed in pregnant uterus and myoma are due to the lower or higher protein expression of the PAF-AH isoform I, especially the alpha2 and/or ss subunits. The decrease of the uterine PAF-AH activity in the late stage of pregnancy may facilitate the action of PAF to stimulate myometrial contraction.
Yasuda
K
K
Department of Obstetrics and Gynecology, Department of Medical Chemistry, Kansai Medical University, Osaka 570-0074, Japan. yasuda@takii.kmu.ac.jp
Okumura
T
T
Okada
H
H
Nakajima
T
T
Aoki
J
J
Arai
H
H
Inoue
K
K
Nishizawa
M
M
Ito
S
S
Kanzaki
H
H
D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase; D000328:Adult; D015153:Blotting, Western; D001921:Brain / Q000196:embryology / Q000201:enzymology; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000032:analysis*; D007668:Kidney / Q000201:enzymology; D007889:Leiomyoma / Q000201:enzymology*; D009215:Myometrium / Q000201:enzymology; D010741:Phospholipases A / Q000032:analysis* / Q000378:metabolism; D011247:Pregnancy; D014590:Uterine Contraction; D014594:Uterine Neoplasms / Q000201:enzymology*; D014599:Uterus / Q000201:enzymology*
D007527:Isoenzymes; D010741:Phospholipases A; D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase