GAP JUNCTION DENSITY IN HUMAN MYOMETRIUM AT TERM REVEALED BY AN ANTIPEPTIDE ANTIBODY AND LASER-SCANNING CONFOCAL MICROSCOPY

The concept that the progesterone-estrogen ratio determines gap juncti on abundance in myometrium has developed from studies in laboratory an imals. In the humans, however, gap junctions form in abundance at term despite a high progesterone-estrogen ratio. We have therefore examine d the relationship between contractile activity, progesterone and estr ogen levels and gap junction abundance in human myometrium at term. My ometrial tissue obtained from women who had an elective or emergency C esarean operation at the 38th or 39th week of pregnancy was immunohist ochemically examined using a polyclonal antiserum raised against a syn thetic peptide matching part of the sequence of connexin43, the princi pal component of myometrial gap junctions. The concentration of proges terone and estradiol in the maternal blood was measured by means of ra dio-immunoassay. The number of gap junctions was estimated by counting of punctate staining patterns obtained in myometrial tissue as viewed by laser confocal microscopy and calculated per 1mum3 of tissue. The number of gap junctions measured was found to be related to the presen ce or absence of labor. In the myometrium of women in labor (active ph ase), the number of gap junctions was highest (45.25 +/- 35). When the myometrium was not contracting (non-labor) and when contractions were weak (pre-labor) the number of gap junctions was low (15.16 +/- 10-5. 75 +/- 5). In the pre-and active phase of labor, the concentration of progesterone in maternal blood was significantly higher (P<0.025 and 0 .03, respectively) than in women who were not in labor. The present st udy shows the potential of using optical section series obtained by la ser confocal microscopy for the quantification and mapping of the thre e-dimensional distribution of pp junctions in human myometrium at term .