In vitro effect of Hepes buffer on maintaining the number of gap junction plaques in human myometrium at term.

In human myometrium, at various stages of labour and in correlation with the concentration of progesterone and estradiol in maternal blood the formation of gap junctions has been described previously by electron microscopy and laser confocal microscopy of immunohistochemically stained myometrial sections. The present investigation focused on the effect of continuous exposure of isolated human myometrium at term to Hepes buffer, on the number of gap junction plaques. Biopsies of myometrium were obtained from 5 pregnant women at term: they had an elective caesarean operation in the 37th or 40th week of pregnancy. The biopsies were immersed immediately in Hepes buffer, trimmed under a stereo microscope into small strips and kept in warm (37 degrees C) oxygenated Hepes buffer supplemented with glucose (0.01 mM). Then some strips of myometrium were incubated at 37 degrees C for 10, 20, 40, 55, and 180 min. The number of gap junction plaques were counted: it decreased in strips of myometrium after 10, 20, 40, 55, and 180 min of in vitro experiment (P < 0.01 vs control). In some of our experiments, the decrease in quantity of gap junction plaques was very dramatic and far below 50% of their numbers found in control specimens but never reached the zero value.