MORPHOMETRIC ANALYSIS OF GAP JUNCTION DENSITY INHUMAN MYOMETRIUM AT TERM

In the human myometrium, the formation of gap junctions in the various stages of labor and, in correlation with the concentration of progest erone in the maternal blood, has not been described adequately. The ac cepted hypothesis that raised concentrations of progesterone in matern al blood in animals prevent the formation of gap junctions was scrutin ized in human myometrium. Myometrial tissue was examined by electron m icroscopy for the presence of gap junctions and analyzed morphometrica lly in 17 women who had an elective or emergency cesarean operation at the 38th or 39th week of pregnancy. The concentrations of progesteron e and estradiol in the maternal and cord blood was measured by means o f radioimmunoassay. The frequency and area of gap junctions varied in relation to the presence or absence of labor. In the myometrium of wom en in labor, gap junctions were most frequent (5.2/1000 mu m of cell m embrane), their area largest (0.32 mu m(2)/1000 mu m of cell membrane) and their fractional area greatest (0.20%). When the women were not i n genuine labor or when contractions were weak, the percentage fractio nal areas of gap junctions were low (0.020-0.090) and the gap junction s very small. In the pre- and active phases of labor, the concentratio n of progesterone in maternal blood was significantly higher (p<0.025 and 0.03 respectively) than in women who were not in labor. Hence, des pite high concentrations of progesterone in the maternal and cord bloo d at term, the myometrium presented numerous gap junctions of relative ly large area.