EDN1 and cardiac hypertrophy: While the mechanism of action of ET-1 on cardiac hypertrophy still remains elusive, we were able to show that 1) the addition of ET-1 during the culture of intact muscle preparations in the absence of preload leads to an increase in the size and force production of that muscle over time, indicating a hypertrophic response, 2) Na+-Ca2+ exchanger, CaMKII, and MAPK are involved in both inotropic and hypertrophic effects of ET-1, and 3) there is only a weak association between ET-1 induced inotropic and hypertrophic response and ERK 1/2 activation.