ADENOSINE-STIMULATED INTRACELLULAR CALCIUM INCREASE IN CULTURED HUMANUTERINE MYOCYTE

The effect of adenosine on intracellular free calcium concentration ([ Ca2+](i)) was studied in human uterine myocyte. Adenosine 10(-6) M eli cited a rapid followed by a maintained increase in [Ca2+](i) in Fluo-3 -loaded myocytes, Compared with basal [Ca2+](i) level, adenosine induc ed a 2.6-fold increase in the absence of extracellular calcium, and a 2.4-fold increase in the presence of extracellular calcium, There was no significant difference between the two groups in the initial respon se, After depletion of intracellular calcium stores by repetitive caff eine(10 mM) applications, adenosine could not induce increase in [Ca2](i), The initial rise could be induced in the absence of extracellula r calcium, whereas the maintained phase after 120 s of adenosine appli cation was dependent on the presence of extracellular calcium, The mai ntained phase response was 1.39- and 0.90-fold compared with basal [Ca 2+](i) level in the presence and absence of extracellular calcium resp ectively, There was significant (p < 0.01) maintenance of [Ca2+](i) in the presence of extracellular calcium, which appeared to be associate d with calcium influx, The data suggest that in human uterine myocytes , adenosine stimulates release of Ca2+ from intracellular stores and i nflux of extracellular Ca2+ through Ca2+ entry pathway.