OXYTOCIN-EVOKED REPETITIVE RISES OF INTRACELLULAR CALCIUM IN SINGLE CULTURED HUMAN MYOMETRIAL CELLS

Repetitive transient increases in intracellular calcium were recorded in single cultured human myometrial cells exposed continuously to oxyt ocin (1 pM-1 nM). Each transient was preceded by a pacemaker-like grad ual increase in baseline [Ca2+]i. Removal of extracellular Ca2+ revers ibly stopped the transients although small fluctuations in [Ca2+]i wer e observed in seven out of eleven cells studied. In a proportion of ce lls (1-2 %) repetitive Ca2+ transients were observed in the absence of exogenous oxytocin. The pattern of activity was similar to that seen in cells exposed to oxytocin. These spontaneous elevations in [Ca2+]i were reversibly inhibited by removing extracellular calcium. These exp eriments demonstrate for the first time repetitive agonist-induced and spontaneous transient increases in [Ca2+]i in single cultured human m yometrial cells.