Human embryonic stem cell-derived cardiomyocytes can mobilize 1,4,5-inositol trisphosphate-operated [Ca2+]i stores: the functionality of angiotensin-II/endothelin-1 signaling pathways.

Because previous findings showed that in human embryonic stem cell-derived cardiomyocytes (hESC-CM) the machinery for Ca2+-induced release of calcium is immature, we tested the hypothesis that hESC-CM contain functional 1,4,5-inositol triphosphate (IP3)-operated intracellular Ca2+ ([Ca2+]i) stores. We investigated the effects of angiotensin II (AT-II) and endothelin 1 (ET-1), which activate the 1,4,5-IP3 pathway, on [Ca2+]i transients and contractions in hESC-CM. Our major findings were that in hESC-CM, both AT-II (10(-9)-10(-7) M) and ET-1 (10(-9)-10(-7) M) exert inotropic and lusitropic effects.