Intracellular calcium of longitudinal muscles isolated from pregnant rat myometrium

Abstract Longitudinal muscle cells were successfully isolated from pregnant rat myometrium (21 days of gestation) with more than a 95% survival rate. The approximate size of relaxed cells was 232.2 ± 74 μm in length and 16.2 ± 7.0 μm in width. Using the fluorescent indicator Fura-2, the concentration of intracellular free calcium ([Ca p2+ ] i ) in resting state cells was calculated to be 116 ± 18.5 nM. The isolated cells responded well to K + , acetylcholine and oxytocin in terms of contraction as well as the increase in [Ca p2+ ] i . The increase in [Ca p2+ ] i induced by acetylcholine and K + appeared to be mainly due to an influx of extracellular Ca p2+ . On the other hand, the oxytocin-induced increase in [Ca p2+ ] i was mainly due to a release of Ca p2+ from intracellular storage sites in the isolated cells. Isolated longitudinal muscle cells can serve as a useful tool in establishing the relationship between [Ca p2+ ] i and regulation of the uterine contraction at the final stage of pregnancy.