Effects of thapsigargin in normal and pretreated with ryancrdine guinea pig cardiomyocytes

Janiak. Effects of thapsigargin in normal and pretreated with ryanodine guinea pig cardiomyocytes. Am. J. PhysioZ. 266 (Heart Circ. Physiol. 35): H1829-H1839, 1994.We com-pared the effects of thapsigargin (TG), a selective blocker of Ca2+-adenosinetriphosphatase of sarcoplasmic reticulum (SR), and ryanodine (Ry) in the single isolated myocytes of guinea pig ventricular myocardium loaded with indo 1 acetoxymethyl ester (AM). TG (2 x 10m7 M) inhibited the rapid phase of Ca2+ transient, increased time to peak intracellular Ca2+ concentra-tion ([Ca2+]) from 158 + 12 to 391 + 60 ms and decreased the--total amplitude of the transient to 89 * 4 % of the pre-TG control. Time to peak of contractions increased from 350 * 47 to 410 * 37 ms and total duration from 666 t 62 to 850 t 198 ms. Total amplitude of contractions was hardly affected. In the cells not loaded with indo l-AM TG decreased the amplitude o